| some properties of a functional reconstituted plasmalemma h-atpase activated by fusicoccin. | fusicoccin was shown to stimulate the atp-driven, intravesicular acidification of liposomes reconstituted with crude fusicoccin receptors and the h(+)-translocating atpase, both solubilized from maize (zea mays l.) plasma membrane. the present paper reports optimal conditions for dual reconstitution and fusicoccin activation as well as the biochemical characterization of the effect of fusicoccin on this system. fusicoccin stimulation of proton pumping was dependent on ph and fusicoccin concentra ... | 1992 | 16668723 |
| oxidation and reduction of sulfite by chloroplasts and formation of sulfite addition compounds. | after exposing intact chloroplasts isolated from spinach (spinacia oleracea l. cv yates) and capable of photoreducing co(2) at high rates to different concentrations of radioactive sulfite in the light or in the dark, (35)so(2) and h(2) (35)s were removed from the acidified suspensions in a stream of nitrogen. remaining activity could be fractionated into sulfate, organic sulfides, and sulfite addition compounds. when chloroplast suspensions contained catalase, superoxide dismutase and o-acetyls ... | 1992 | 16668703 |
| stromal ph and photosynthesis are affected by electroneutral k and h exchange through chloroplast envelope ion channels. | potassium movement across the limiting membrane of the chloroplast inner envelope is known to be linked to counterex-change of protons. for this reason, k(+) efflux is known to facilitate stromal acidification and the resultant photosynthetic inhibition. however, the specific nature of the chloroplast envelope proteins that facilitate k(+) fluxes, and the biophysical mechanism which links these cation currents to h(+) counterflux, is not characterized. it was the objective of this work to elucid ... | 1992 | 16668693 |
| decrease of nitrate reductase activity in spinach leaves during a light-dark transition. | in leaves of spinach plants (spinacia oleracea l.) performing co(2) and no(3) (-) assimilation, at the time of sudden darkening, which eliminates photosystem i-dependent nitrite reduction, only a minor temporary increase of the leaf nitrite content is observed. because nitrate reduction does not depend on redox equivalents generated by photosystem i activity, a continuation of nitrate reduction after darkening would result in a large accumulation of nitrite in the leaves within a very short time ... | 1992 | 16668679 |
| adenine nucleotides are apparently involved in the light-dark modulation of spinach-leaf nitrate reductase. | nitrate reductase (nr; ec 1.6.6.1) in spinach (spinacia oleracea l. cv. polka f1) leaves showed reversible modulation, being activated in the light and inactivated in the dark (t/2 = 20-30 min). the large changes in enzyme activity during light-dark transients were observed only when assayed in buffers containing free mg(2+). in the presence of edta (5 mm), the enzyme activity was high and the light modulation was barely evident.the inactivation of nr in the dark could be totally prevented by an ... | 1992 | 24186663 |
| ribulose-1,5-bisphosphate carboxylase-oxygenase, other calvin-cycle enzymes, and chlorophyll decrease when glucose is supplied to mature spinach leaves via the transpiration stream. | the inhibition of photosynthesis after supplying glucose to detached leaves of spinach (spinacia oleracea l.) was used as a model system to search for mechanisms which potentially contribute to the "sink" regulation of photosynthesis. detached leaves were supplied with 50 mm glucose or water for 7 d through the transpiration stream, holding the leaves in low irradiance (16 μmol photons · m(-2) · s(-1)) and a cycle of 9 h light/15 h darkness to prevent any endogenous accumulation of carbohydrate. ... | 1991 | 24186575 |
| adpg formation by the adp-specific cleavage of sucrose-reassessment of sucrose synthase. | the standardized enzyme coupling method for assaying sucrose synthase activities in the direction of sucrose cleavage was reexamined using enzyme preparations from cultured cells of sycamore (acer pseudoplatanus l.) and spinach leaves (spinacea oleracea). both atp and tris, commonly utilized in assay systems to measure sucrose synthase, were found to inhibit non-competitively the adpg-synthesizing activities of the enzyme. upon substituting atp by either gtp or utp, and tris by hepes, we found t ... | 1991 | 1834479 |
| surface charge-mediated effects of mg on k flux across the chloroplast envelope are associated with regulation of stromal ph and photosynthesis. | studies of spinacia oleracea l. were undertaken to characterize further how mg(2+) external to the isolated intact chloroplast interacts with stromal k(+), ph, and photosynthetic capacity. data presented in this report were consistent with the previously developed hypothesis that millimolar levels of external, unchelated mg(2+) result in lower stromal k(+), which somehow is linked to stromal acidification. stromal acidification directly results in photosynthetic inhibition. these effects were at ... | 1991 | 16668438 |
| tandem mass spectrometry identifies sites of three post-translational modifications of spinach light-harvesting chlorophyll protein ii. proteolytic cleavage, acetylation, and phosphorylation. | the photosynthetic membranes of spinach (spinacia oleracea l.) chloroplasts were incubated with [gamma-32p] atp. when the thylakoid membrane kinase was activated with light, the 25- and 27-kda forms of the light-harvesting chlorophyll a/b protein (lhc ii) were phosphorylated on their amino termini. treatment of the membranes with proteinase k or thermolysin released phosphopeptides which were purified by ferric ion affinity chromatography and reverse phase high performance liquid chromatography. ... | 1991 | 1894641 |
| properties of oxidized and reduced spinach (spinacia oleracea) chloroplast fructose-1,6-bisphosphatase activated by various agents. | fructose-1,6-bisphosphatase (fbpase) can be reduced and activated by either dithiothreitol or reduced thioredoxin. this activation is ph-dependent. an amino acid group with a pk value of 5.55 is involved in this process. both enzyme forms can also be stimulated by agents such as fructose 1,6-bisphosphate, mg2+, ca2+ and ca2+/fructose 1,6-bisphosphate. fbpase reduced by dithiothreitol is more strongly activated than the enzyme reduced by thioredoxin. the specificity constant (kcat./km) is enhance ... | 1991 | 1654892 |
| multiplicity of soluble glucan-synthase activity in spinach leaves: enzyme pattern and intracellular location. | buffer-extractable proteins from leaves of spinacia oleracea l. were separated by non-denaturing polyacrylamide gel electrophoresis. gels were stained for adenosine diphosphoglucose (adpglucose)-dependent glucan-synthase (gs) activity (ec 2.4.1.21). three major forms of activity were observed. no staining was detectable when adpglucose was replaced by an equimolar concentration of either uridine, guanosine or cytosine diphosphoglucose. two of the three gs forms exhibited both primed and citrate- ... | 1991 | 24186345 |
| amino acid and sucrose content determined in the cytosolic, chloroplastic, and vacuolar compartments and in the phloem sap of spinach leaves. | amino acid and sucrose contents were analyzed in the chloroplastic, cytosolic, and vacuolar compartments and in the phloem sap of illuminated spinach leaves (spinacia oleracea l.). the determination of subcellular metabolite distribution was carried out by nonaqueous fractionation of frozen and lyophilized leaf material using a novel three-compartment calculation method. the phloem sap was collected by aphid stylets which had been severed by a laser beam. subcellular analysis revealed that the a ... | 1991 | 16668375 |
| effect of microtubule stabilization on the freezing tolerance of mesophyll cells of spinach. | freezing, dehydration, and supercooling cause microtubules in mesophyll cells of spinach (spinacia oleracea l. cv bloomsdale) to depolymerize (me bartolo, jv carter, plant physiol [1991] 97: 175-181). the objective of this study was to determine whether the lt(50) (lethal temperature: the freezing temperature at which 50% of the tissue is killed) of spinach leaf tissue can be changed by diminishing the extent of microtubule depolymerization in response to freezing. also examined was how toleranc ... | 1991 | 16668367 |
| microtubules in mesophyll cells of nonacclimated and cold-acclimated spinach : visualization and responses to freezing, low temperature, and dehydration. | responses of cortical microtubules in spinach (spinacia oleracea l. cv bloomsdale) mesophyll cells to freezing, thawing, supercooling, and dehydration were assessed. microtubules were visualized using a modified procedure for indirect immunofluorescence microscopy. leaf sections of nonacclimated and cold-acclimated spinach were slowly frozen to various temperatures, fixed while frozen, and microtubules immunolabelled. both nonacclimated and cold-acclimated cells exhibited nearly complete microtu ... | 1991 | 16668366 |
| six independent losses of the chloroplast dna rpl2 intron in dicotyledons: molecular and phylogenetic implications. | previous studies have shown that in several angiosperms and the liverwort marchantia the chloroplast gene rpl2, encoding ribosomal protein l2, is interrupted by an intron, but that in spinach (spinacia oleracea, caryophyllales) this intron has been lost. we have determined the distribution of the rpl2 intron for 390 species representing 116 angiosperm families. filter hybridizations reveal that the intron is absent from the chloroplast genomes of all examined families of the caryophyllales, sugg ... | 1991 | 28564183 |
| solubilization, partial purification, and reconstitution of the glycolate/glycerate transporter from chloroplast inner envelope membranes. | the glycolate/glycerate transporter of spinach (spinacia oleracea l.) chloroplast inner envelope membranes was solubilized by treatment of the membranes with sodium cholate. mixtures of the cholate extracts and soy asolectin were subjected to gel filtration to remove the detergent. the reconstituted vesicles were frozen, thawed, and sonicated in a buffer that contained 10 millimolar d-glycerate and, usually, [(3)h]sucrose as an internal space indicator. the dilution of the vesicles into a medium ... | 1991 | 16668298 |
| regulation by ca of a cytosolic fructose-1,6-bisphosphatase from spinach leaves. | cytosolic fructose-1,6-bisphosphatase from spinach (spinacia oleracea l.) leaves was purified over 1700-fold. the final preparation was specific for fructose-1,6-bisphosphate in the presence of either mg(2+) or mn(2+), and was free of interfering enzyme activities. ca(2+) was an effector of fructose-1,6-bisphosphatase activity, and showed different kinetics, depending on whether mg(2+) or mn(2+) was used as cofactor. in the presence of 5 millimolar mg(2+), ca(2+) appeared as activator or as inhi ... | 1991 | 16668293 |
| compartmentation studies on spinach leaf peroxisomes : evidence for channeling of photorespiratory metabolites in peroxisomes devoid of intact boundary membrane. | in concurrence with earlier results, the following enzymes showed latency in intact spinach (spinacia oleracea l.) leaf peroxisomes: malate dehydrogenase (89%), hydroxypyruvate reductase (85%), serine glyoxylate aminotransferase (75%), glutamate glyoxylate aminotransferase (41%), and catalase (70%). in contrast, glycolate oxidase was not latent. aging of peroxisomes for several hours resulted in a reduction in latency accompanied by a partial solubilization of the above mentioned enzymes. the ex ... | 1991 | 16668283 |
| acyl carrier protein is conjugated to glutathione in spinach seed. | acyl carrier protein (acp) contains an essential sulfhydryl group in its phosphopantetheine prosthetic group. we have investigated the state of this sulfhydryl in developing and mature spinach seed (spinacia oleracea). seed extracts were separated on sodium dodecyl sulfate or native polyacrylamide gels, blotted to nitrocellulose, and probed with antibodies raised against spinach acp-i. in extracts of mature seeds prepared with reducing agents, acp-ii migrated as a single major band, whereas extr ... | 1991 | 16668278 |
| purification of udp-galactose: diacylglycerol galactosyltransferase from chloroplast envelopes of spinach (spinacia oleracea l.). | uridine 5'-diphosphate(udp)-galactose: 1,2-diacylglycerol 3-o-β-d-galactopyranosyltransferase (ec 2.4.1.46) is an integral protein of chloroplast envelope membranes from which it has been partially purified (covès et al., 1986, febs lett. 208, 401-406). we have worked out a purification procedure which after removal of peripheral membrane proteins, solubilization and two chromotographic steps allowed us to identify a 22-kda protein as the galactosyltransferase. enrichment of enzymatic activity w ... | 1991 | 24194148 |
| symport of proton and sucrose in plasma membrane vesicles isolated from spinach leaves. | the mechanism of sucrose transport was investigated in plasma membrane (pm) vesicles isolated from spinach (spinacia oleracea l.) leaves. pm vesicles were isolated by aqueous two-phase partitioning and were equilibrated in ph 7.8 buffer containing k(+). the vesicles rapidly accumulated sucrose in the presence of a transmembrane ph gradient (deltaph) with external ph set at 5.8. the uptake rate was slow at ph 7.8. the k(+)-selective ionophore, valinomycin, stimulated uptake in the presence of a d ... | 1991 | 16668230 |
| spinach leaf acetyl-coenzyme a synthetase: purification and characterization. | acetyl-coenzyme a (coa) synthetase was purified 364-fold from leaves of spinach (spinacia oleracea l.) using ammonium sulfate fractionation followed by ion exchange, dye-ligand, and gel permeation chromatography. the final specific activity was 2.77 units per milligram protein. the average m(r) value of the native enzyme was about 73,000. the michaelis constants determined for mg-atp, acetate, and coenzyme a were 150, 57, and 5 micromolar, respectively. the purified enzyme was sensitive to subst ... | 1991 | 16668197 |
| rapid modulation of spinach leaf nitrate reductase by photosynthesis : ii. in vitro modulation by atp and amp. | assimilatory nitrate reductase activity (nra) in crude spinach leaf (spinacia oleracea) extracts undergoes rapid changes following fluctuations in photosynthesis brought about by changes in external co(2) or by water stress (wm kaiser, e brendle-behnisch [1991] plant physiol 96:363-367). a modulation of nra sharing several characteristics (stability, response to mg(2+) or ca(2+), kinetic constants) with the in vivo modulation was obtained in vitro by preincubating desalted leaf extracts with phy ... | 1991 | 16668195 |
| rapid modulation of spinach leaf nitrate reductase activity by photosynthesis : i. modulation in vivo by co(2) availability. | it has been shown recently that in spinach leaves (spinacia oleracea) net photosynthesis and nitrate reduction are closely linked: when net photosynthesis was low because of stomatal closure, rates of nitrate reduction decreased (wm kaiser, j förster [1989] plant physiol 91: 970-974). here we present evidence that photosynthesis regulates nitrate reduction by modulating nitrate reductase activity (nra, ec 1.6.6.1). when spinach leaves were exposed to low co(2) in the light, extractable nra decli ... | 1991 | 16668194 |
| oxalate as a potent and selective inhibitor of spinach (spinacia oleracea) leaf nadph-dependent hydroxypyruvate reductase. | purified spinach (spinacia oleracea) nadph-preferring hydroxypyruvate reductase (hpr-2) was potently and selectively inhibited by oxalate, an end product of metabolism in plants. both hydroxypyruvate- and glyoxylate-dependent rates of the hpr-2 enzyme were affected. oxalate acted as an uncompetitive inhibitor of the enzyme, with ki values of 7 and 36 microm for the nadph/hydroxypyruvate and nadph/glyoxylate pairs of reactants respectively. oxalate, at millimolar levels, caused less than 10% inhi ... | 1991 | 2039466 |
| photosynthetic oxygen evolution and chlorophyll fluorescence in intact isolated chloroplasts on a solid support: the influence of orthophosphate. | we devised recently a method to trap intact isolated chloroplasts on a solid support consisting of membrane filters made of cellulose nitrate (cerović et al., 1987, plant physiol. 84, 1249-1251). the addition of alkaline phosphatase to the reaction medium enabled continuous photosynthesis by spinach (spinacia oleracea l.) chloroplasts to be sustained by hydrolysis of newly produced and exported triose phosphates and recycling of orthophosphate. in this system, simultaneous measurements of chloro ... | 1991 | 24194077 |
| protection of tryptic-sensitive sites in the large subunit of ribulosebisphosphate carboxylase/oxygenase by catalysis. | limited tryptic proteolysis of spinach (spinacia oleracea) ribulose bisphosphate carboxylase/oxygenase (ribulose-p(2) carboxylase) resulted in the ordered release of two adjacent n-terminal peptides from the large subunit, and an irreversible, partial inactivation of catalysis. the two peptides were identified as the n-terminal tryptic peptide (acetylated pro-3 to lys-8) and the penultimate tryptic peptide (ala-9 to lys-14). kinetic comparison of hydrolysis at lys-8 and lys-14, enzyme inactivati ... | 1991 | 16668178 |
| biosynthesis and desaturation of prokaryotic galactolipids in leaves and isolated chloroplasts from spinach. | mono- and digalactosyldiacylglycerol (mgdg and dgdg) were isolated from the leaves of sixteen 16:3 plants. in all of these plant species, the sn-2 position of mgdg was more enriched in c(16) fatty acids than sn-2 of dgdg. the molar ratios of prokaryotic mgdg to prokaryotic dgdg ranged from 4 to 10. this suggests that 16:3 plants synthesize more prokaryotic mgdg than prokaryotic dgdg. in the 16:3 plant spinacia oleracea l. (spinach), the formation of prokaryotic galactolipids was studied both in ... | 1991 | 16668143 |
| coaction of light, nitrate and a plastidic factor in controlling nitrite-reductase gene expression in spinach. | it is well established that nitrite reductase (nir; ec 1.7.7.1) a key enzyme of nitrate reduction - is "induced" by nitrate and light. in the present study with the spinach (spinacia oleracea l.) seedling the dependency of nir appearance on nitrate, light and a 'plastidic factor' was investigated to establish the nature of the coaction between these controlling factors. a cdna clone coding for spinach nir was available as a probe. the major results we have obtained are the following: (i) the lig ... | 1991 | 24193932 |
| studies on the system regulating proton movement across the chloroplast envelope : effects of atpase inhibitors, mg, and an amine anesthetic on stromal ph and photosynthesis. | studies were undertaken to further characterize the spinach (spinacea oleracea) chloroplast envelope system, which facilitates h(+) movement into and out of the stroma, and, hence, modulates photosynthetic activity by regulating stromal ph. it was demonstrated that high envelope-bound mg(2+) causes stromal acidification and photosynthetic inhibition. high envelope-bound mg(2+) was also found to necessitate the activity of a digitoxinand oligomycin-sensitive atpase for the maintenance of high str ... | 1991 | 16668116 |
| redox transfer across the inner chloroplast envelope membrane. | in leaves of spinach plants (spinacia oleracea l.) grown in ambient co(2) the subcellular contents of adenylates, pyridine nucleotides, 3-phosphoglycerate, dihydroxyacetone phosphate, malate, glutamate, 2-oxoglutarate, and aspartate were assayed in the light and in the dark by nonaqueous fractionation technique. from the concentrations of nadp and nadph determined in the chloroplast fraction of illuminated leaves the stromal nadph to nadp ratio is calculated to be 0.5. for the cytosol a nadh to ... | 1991 | 16668101 |
| the relationship between the activation state of sucrose-phosphate synthase and the rate of co2 assimilation in spinach leaves. | the relationship between the gas-exchange characteristics of spinach (spinacia oleracea l.) leaves and the activation state of sucrose-phosphate synthase was examined at different intercellular partial pressures of co2 at two different photon flux densities. there was a strong positive correlation between the activation state of sucrose-phosphate synthase and the assimilation rate. the relationship was the same at both photon flux densities, indicating that the activation state of the enzyme is ... | 1991 | 24193857 |
| inhibition of the transthylakoid gradient of electrochemical proton potential by the local anesthetic dibucaine. | the effects of the local anesthetic dibucaine on coupling between electron transport and atp synthesis-hydrolysis by the coupling-factor complex (cf0cf1 atpase) were investigated in thylakoid membranes from spinacia oleracea l. cv. monatol. evidence is presented that inhibition of atp synthesis was produced by a specific uncoupling mechanism which was based on dibucaine-membrane surface interactions rather than on the interaction of dibucaine with the atpase complex. dibucaine reduced the osmoti ... | 1991 | 24193850 |
| in vitro phosphorylation and inactivation of spinach leaf sucrose-phosphate synthase by an endogenous protein kinase. | (1) partially purified preparations of spinach (spinacia oleracea l.) leaf sucrose-phosphate synthase (sps) contain an endogenous protein kinase that phosphorylates and inactivates the enzyme with [gamma-32p]atp. (2) the kinetic effect of phosphorylation is to alter affinities for substrates and the effector inorganic phosphate without affecting maximum velocity. (3) two-dimensional peptide mapping of tryptic digests of in vitro labeled sps yielded two phosphopeptides (designated sites 5 and 7). ... | 1991 | 1825791 |
| nonsteady-state photosynthesis following an increase in photon flux density (pfd) : effects of magnitude and duration of initial pfd. | the response of photosynthesis to an increase in photon flux density (pfd) from low to higher pfd was investigated using spinach (spinacia oleracea l.). the time-course for this response was qualitatively similar to that observed for a dark-to-high-pfd transition, showing an initial, rapid increase in photosynthesis over the first minute or so, followed by a slower increase lasting 5 to 10 minutes. this slow increase was approximately exponential and could be linearized using a semilogarithmic p ... | 1991 | 16668012 |
| formation of the fe-s cluster of ferredoxin in lysed spinach chloroplasts. | in vitro formation of the (35)s-labeled fe-s cluster of ferredoxin (fd) has been achieved by incubating apo-fd and [(35)s]cysteine with osmotically lysed chloroplasts of spinach (spinacia oleracea). correct integration of the (35)s-labeled fe-s cluster into fd was verified on the basis of the following: (a) under nondenaturing conditions, (35)s-labeled holo-fd showed the same electrophoretic mobility as authentic holo-fd; (b) (35)s-labeled holo-fd showed an ability to bind fd-nadp(+) reductase; ... | 1991 | 16667987 |
| inactivation of highly activated spinach leaf sucrose-phosphate synthase by dephosphorylation. | spinach (spinacia oleracea l.) leaf sucrose-phosphate synthase (sps) can be phosphorylated and inactivated in vitro with [gamma-(32)p]atp (jla huber, sc huber, th nielsen [1989] arch biochem biophys 270: 681-690). thus, it was surprising to find that sps, extracted from leaves fed mannose in the light to highly activate the enzyme, could be inactivated in an atp-independent manner when desalted crude extracts were preincubated at 25 degrees c before assay. the "spontaneous" inactivation involved ... | 1991 | 16667968 |
| isolation of a cdna clone for spinach lipid transfer protein and evidence that the protein is synthesized by the secretory pathway. | a cdna clone encoding a nonspecific lipid transfer protein from spinach (spinacia oleracea) was isolated by probing a library with synthetic oligonucleotides based on the amino acid sequence of the protein. determination of the dna sequence indicated a 354-nucleotide open reading frame which encodes a 118-amino acid residue polypeptide. the first 26 amino acids of the open reading frame, which are not present in the mature protein, have all the characteristics of a signal sequence which is norma ... | 1991 | 16667945 |
| roles of atp and nadph in formation of the fe-s cluster of spinach ferredoxin. | ferredoxin (fd) in higher plants is encoded by a nuclear gene, synthesized in the cytoplasm as a larger precursor, and imported into the chloroplast, where it is proteolytically processed, and assembled with the [2fe-2s] cluster. the final step in the biosynthetic pathway of fd can be analyzed by a reconstitution system composed of isolated chloroplasts and [(35)s]cysteine, in which [(35)s]sulfide and iron are incorporated into fd to build up the (35)s-labeled fe-s cluster. although a lysed chlo ... | 1991 | 16667935 |
| binding of the recombinant proteinase inhibitor eglin c, of the soybean bowman-birk proteinase inhibitor and of its chymotrypsin and trypsin inhibiting fragments to leu-proteinase, the leucine specific serine proteinase from spinach (spinacia oleracea l.) leaves: thermodynamic study. | the effect of ph and temperature on the apparent association equilibrium constant (ka) for the binding of the recombinant proteinase inhibitor eglin c (eglin c), of the soybean bowman-birk proteinase inhibitor (bbi) and of its chymotrypsin and trypsin inhibiting fragments (f-c and f-t, respectively) to leu-proteinase, the leucine specific serine proteinase from spinach (spinacia oleracea l.) leaves, has been investigated. on lowering the ph from 9.5 to 4.5, values of ka (at 21 degrees c) for com ... | 1991 | 1669829 |
| effect of growth temperature and temperature shifts on spinach leaf morphology and photosynthesis. | the growth kinetics of spinach plants (spinacia oleracea l. cv savoy) grown at 5 degrees c or 16 degrees c were determined to allow us to compare leaf tissues of the same developmental stage rather than chronological age. the second leaf pairs reached full expansion at a plant age of 32 and 92 days for the 16 degrees c and 5 degrees c plants, respectively. growth at 5 degrees c resulted in an increased leaf area, dry weight, dry weight per area, and leaf thickness. despite these changes, pigment ... | 1990 | 16667923 |
| desaturation of oleoyl groups in envelope membranes from spinach chloroplasts. | envelope membranes isolated from chloroplasts of spinach (spinacia oleracea) desaturate oleoyl groups in monogalactosyl diacylglycerol to linoleoyl groups. the desaturation requires nadph in combination with ferredoxin and is not restricted to monogalactosyl diacylglycerol, since it is also observed in biosynthetic intermediates as, for example, in phosphatidic acid. this indicates a certain degree of unspecificity of the oleate desaturase in isolated envelope membranes. lipid desaturation is an ... | 1990 | 11607123 |
| novel forms of ferredoxin and ferredoxin-nadp reductase from spinach roots. | ferredoxin and the enzyme catalyzing its reduction by nadph, ferredoxin-nadp reductase (ferredoxin-nadp+ oxidoreductase or fnr), were found to be present in roots of spinach (spinacia oleracea). localization experiments with endosperm of germinating castor beans (ricinus communis), a classical nonphotosynthetic tissue for cell fractionation studies, confirmed that ferredoxin and fnr are localized in the plastid fraction. both proteins were purified from spinach roots and found to resemble their ... | 1990 | 2241175 |
| localization of atp sulfurylase and o-acetylserine(thiol)lyase in spinach leaves. | the intracellular compartmentation of atp sulfurylase and o-acetylserine(thiol)lyase in spinach (spinacia oleracea l.) leaves has been investigated by isolation of organelles and fractionation of protoplasts. atp sulfurylase is located predominantly in the chloroplasts, but is also present in the cytosol. no evidence was found for atp sulfurylase activity in the mitochondria. two forms of atp sulfurylase were separated by anion-exchange chromatography. the more abundant form is present in the ch ... | 1990 | 16667839 |
| activation of sucrose-phosphate synthase from darkened spinach leaves by an endogenous protein phosphatase. | sucrose-phosphate synthase (sps; ec 2.4.1.14) extracted from darkened spinach (spinacia oleracea l.) leaves has a low activation state, defined as the ratio of activity measured with limiting substrates (plus the inhibitor pi) to activity with saturating substrates (maximum velocity). preincubation at 25 degrees c of desalted crude extracts from darkened leaves resulted in a time-dependent increase in activation state that was inhibited by pi [ic50 (concentration causing 50% inhibition) approxim ... | 1990 | 2173486 |
| free fatty acids regulate two galactosyltransferases in chloroplast envelope membranes isolated from spinach leaves. | effects of mgcl(2) and free fatty acids (ffa) on galactolipid:galactolipid galactosyltransferase (gggt) and udp-galactose: 1,2-diacylglycerol galactosyltransferase (udgt) in chloroplast envelope membranes isolated from spinach (spinacia oleracea l.) leaves were examined. gggt activity was sigmoidally stimulated by mgcl(2) with a saturated concentration of more than 5 millimolar. free alpha-linolenic acid (18:3) caused a drastic increase in gggt activity under limiting concentrations of mgcl(2), ... | 1990 | 16667779 |
| pathway for the synthesis of triacylglycerols from monogalactosyldiacylglycerols in ozone-fumigated spinach leaves. | when the upper leaf surface of spinach (spinacia oleracea l.) plants was treated with [1-(14)c]acetate and grown for 2 days, (14)c was effectively incorporated into acyl moieties of leaf lipids in ratios approximately their composition by mass. fumigation of the plants with ozone (0.5 microliter per liter) caused a redistribution of (14)c among lipid classes, i.e. a marked increase of (14)c content in triacylglycerol (tg) and 1,2-diacylglycerol (1,2-dg) and a decrease of label in monogalactosyld ... | 1990 | 16667778 |
| conversion of monogalactosyldiacylglycerols to triacylglycerols in ozone-fumigated spinach leaves. | molecular species and fatty acid distribution of triacylglycerol (tg) accumulated in spinach (spinacia oleracea l.) leaves fumigated with ozone (0.5 microliter per liter) were compared with those of monogalactosyldiacylglycerol (mgdg). analysis of positional distribution of the fatty acids in mgdg and the accumulated tg by the enzymatic digestion method showed that hexadecatrienoate (16:3) was restricted to sn-2 position of the glycerol backbone in both mgdg and tg, whereas alpha-linolenate (18: ... | 1990 | 16667777 |
| freezing of isolated thylakoid membranes in complex media. vi. the effect of ph. | thylakoid membranes isolated from spinach leaves (spinacia oleracea l. cv. monatol) were used as a model biomembrane system for evaluating the significance of the hydrogen ion activity for cryoprotection. after freeze-thaw treatment in a buffered complex medium adjusted to various ph, light-induced photosynthetic membrane reactions were determined at optimum proton concentration. when thylakoids were suspended at hydrogen ion activities above and below the physiologically important ph range, irr ... | 1990 | 2249457 |
| regulation of photosynthetic sucrose synthesis: a role for calcium? | we have investigated whether changes of the cytosolic free-calcium concentration could regulate photosynthetic sucrose synthesis. partially purified enzymes from spinach (spinacea oleracea l.) leaves were assayed using calcium-egta buffers to obtain defined free-calcium concentrations in the low micromolar and submicromolar ranges. these concentrations of calcium did not directly affect sucrose-phosphate synthase activity. they inhibited the cytosolic fructose-1,6-bisphosphatase, acting competit ... | 1990 | 24197102 |
| involvement of ferredoxin in desaturation of lipid-bound oleate in chloroplasts. | intact spinach (spinacia oleracea) chloroplasts, pulse-labeled with [(14)c]acetate, desaturate newly formed fatty acids as ester groups of monogalactosyl diacylglycerol in a subsequent chase in the dark. rupture of pulse-labeled chloroplasts by addition of a detergent solution 3-([3-cholamidopropyl]dimethylammonio)-1-propane sulfonate preserves part of this desaturation activity. direct addition of different free fatty acids together with appropriate cofactors to detergent-ruptured chloroplasts ... | 1990 | 16667689 |
| photoinhibition at chilling temperatures and effects of freezing stress on cold acclimated spinach leaves in the field. a fluorescence study. | the role of high light stress in a natural environment was studied on spinach plants (spinacia oleracea l. cv. wolter) grown in the field during the winter season. fluorescence induction (at 293 k and 77 k) of leaves was used to characterize the stress effects. night frost with minimum temperatures between - 1.5°c and -7.5°c (i.e. above the'frost killing point'at ca. -11.5°c) led to impaired photosynthesis. this was seen as increased initial fluorescence (f(o) ), decreased ratio of variable to m ... | 1990 | 21087269 |
| activity of ribulose 1,5-bisphosphate carboxylase oxygenase as a function of storage conditions. | optimal storage conditions to retain ribulose 1, 5-bisphosphate carboxylase/oxygenase (rubisco) activity were investigated. the soluble spinach (spinacia oleracea) enzyme was pretreated with its activators, mg(2+) and hco(3) (-), and then stored for up to 30 days at 4 or -18 degrees c or in liquid n(2). cold inactivation and conformational changes were suggested to be involved during rubisco storage in the cold, leading to its inactivation. pretreatment of the enzyme with mg(2+) and co(2) and su ... | 1990 | 16667648 |
| light saturation response of inactive photosystem ii reaction centers in spinach. | the effective absorption cross section of inactive photosystem ii (ps ii) centers, which is the product of the effective antenna size and the quantum yield for photochemistry, was investigated by comparing the light saturation curves of inactive ps ii and active reaction centers in intact chloroplasts and thylakoid membranes of spinach (spinacia oleracea). inactive ps ii centers are defined as the impaired ps ii reaction centers that require greater than 50 ms for the reoxidation of qa (-) subse ... | 1990 | 24420169 |
| control of photosynthate partitioning in spinach leaves : analysis of the interaction between feedforward and feedback regulation of sucrose synthesis. | experiments were carried out to estimate the elasticity coefficients and thence the distribution of control of sucrose synthesis and photosynthate partitioning between cytosolic fructose-1,6-bisphosphatase and sucrose-phosphate synthase (sps), by applying the dualmodulation method of kacser and burns (1979, biochem. soc. trans. 7, 1149-1161). leaf discs of spinach (spinacia oleracea l.) were harvested at the beginning and end of the photoperiod and illuminated at five different irradiances to al ... | 1990 | 24196941 |
| carbon metabolism in spinach leaves as affected by leaf age and phosphorus and sulfur nutrition. | spinach (spinacea oleracea) plants were grown either continuously on complete nutrient solutions or for 2 weeks on media deficient in phosphate or sulfate. to characterize leaf carbohydrate metabolism, levels of phosphorylated intermediates, activities of enzymes involved in photosynthetic carbon metabolism, contents of soluble and acid hydrolyzable sugars were measured in leaves differing in age and mineral status and related to leaf rates of photosynthesis and assimilate partitioning. concentr ... | 1990 | 16667581 |
| the aggregation states of spinach phosphoribulokinase. | phosphoribulokinase (prk; ec 2.1.7.19) is active in illuminated chloroplasts and inactive in darkened chloroplasts. this regulatory mechanism is mediated by thioredoxin-dependent reduction of a kinase disulfide in vivo. extracts of spinach (spinacia oleracea l.) leaves in the presence of 10 mm dithiothreitol contain a single 80-kda form of prk as judged by gel filtration. gel filtration of thiol-free extracts of light-harvested tissue shows the presence of two inactive forms of prk, the 80-kda f ... | 1990 | 24196813 |
| shikimate kinase from spinach chloroplasts : purification, characterization, and regulatory function in aromatic amino acid biosynthesis. | shikimate kinase was purified to near homogenity from spinach spinacia oleracea l. chloroplasts and found to consist of a single 31 kilodalton polypeptide. the purified enzyme was unstable, but could be stabilized by a variety of added proteins, including oxidized and reduced thioredoxins. whereas the isolated enzyme was stimulated by mono- and dithiol reagents, the enzyme in intact chloroplasts was unaffected by added thiols and showed only minor response to dark/light transitions. these result ... | 1990 | 16667533 |
| isolation and characterization of the cytosolic and chloroplastic 3-phosphoglycerate kinase from spinach leaves. | the cytosol and chloroplast 3-phosphoglycerate kinases (3-pgk) from spinach (spinacia oleracea l.) were purifled to apparent homogeneity. the procedure included a conventional anion-exchange chromatography on deae-cellulose and mainly a series of hplc columns. the charge differences of the two isoenzymes were so small that separation was only successful by anion-exchange chromatography on a hplc synchropak ax 300 column. the portion of the two isoenzmyes in leaf tissue was estimated as 5% and 95 ... | 1990 | 16667463 |
| status of the substrate binding sites of ribulose bisphosphate carboxylase as determined with 2-c-carboxyarabinitol 1,5-bisphosphate. | the properties of the tight and specific binding of 2-c-carboxy-d-arabinitol 1,5-bisphosphate (cabp), which occurs only to reaction sites of ribulose 1,5-bisphosphate carboxylase (rubisco) that are activated by co(2) and mg(2+), were studied. with fully active purified spinach (spinacia oleracea) rubisco the rate of tight binding of [(14)c]cabp fit a multiple exponential rate equation with half of the sites binding with a rate constant of 40 per minute and the second half of the sites binding at ... | 1990 | 16667442 |
| chlamydomonas reinhardtii phosphoribulokinase : sequence, purification, and kinetics. | the sequence and kinetic properties of phosphoribulokinase purified from chlamydomonas reinhardtii were determined and compared with the spinach (spinacea oleracea) enzyme. chlamydomonas phosphoribulokinase was purified to apparent homogeneity, with a specific activity of 410 micromoles per minute per milligram. polyclonal antibodies to the purified protein were used to isolate a chlamydomonas cdna clone, which, upon sequencing, was found to contain the entire coding region. the transit peptide ... | 1990 | 16667433 |
| regulation of sedoheptulose-1,7-bisphosphatase by sedoheptulose-7-phosphate and glycerate, and of fructose-1,6-bisphosphatase by glycerate in spinach chloroplasts. | using partially purified sedoheptulose-1,7-bisphosphatase from spinach (spinacia oleracea l.) chloroplasts the effects of metabolites on the dithiothreitoland mg(2+)-activated enzyme were investigated. a screening of most of the intermediates of the calvin cycle and the photorespiratory pathway showed that physiological concentrations of sedoheptulose-7-phosphate and glycerate specifically inhibited the enzyme by decreasing its maximal velocity. an inhibition by ribulose-1,5-bisphosphate was als ... | 1990 | 24196680 |
| molecular cloning of a plant betaine-aldehyde dehydrogenase, an enzyme implicated in adaptation to salinity and drought. | many plants, as well as other organisms, accumulate betaine (n,n,n-trimethylglycine) as a nontoxic or protective osmolyte under saline or dry conditions. in plants, the last step in betaine synthesis is catalyzed by betaine-aldehyde dehydrogenase (badh, ec 1.2.1.8), a nuclear-encoded chloroplastic enzyme. a cdna clone for badh (1812 base pairs) was selected from a lambda gt10 cdna library derived from leaves of salt-stressed spinach (spinacia oleracea l.). the library was screened with oligonucl ... | 1990 | 2320587 |
| sensitivity of photosynthesis by spinach chloroplast membranes to osmotic stress in vitro: rapid inhibition of o2 evolution in presence of magnesium. | thylakoids prepared from spinach (spinacea oleracea l.) chloroplasts were exposed to osmotic stress in vitro in the presence or absence of different inorganic salts. by an hour after incubation in 1.0 m sorbitol and 10 mm (or more) mgcl2, the thylakoids lost approximately 80% of their photosystem (ps) ii activity, but not ps i. the inhibition occurred only in presence of magnesium as indicated by the combinations of several cations/anions. the ps ii activity was relatively insensitive to osmotic ... | 1990 | 24419656 |
| oxidation versus reductive detoxification of so(2) by chloroplasts. | intact chloroplasts isolated from spinach (spinacia oleracea l. cv yates) both oxidized and reduced added sulfite in the light. oxidation was fast only when endogenous superoxide dismutase was inhibited by cyanide. it was largely suppressed by scavengers of oxygen radicals. after addition of o-acetylserine, chloroplasts reduced sulfite to cysteine and exhibited sulfite-dependent oxygen evolution. cysteine synthesis from sulfite was faster than from sulfate. the results are discussed in relation ... | 1990 | 16667358 |
| on the regulation of spinach nitrate reductase. | a coupled assay has been worked out to study spinach (spinacea oleracea l.) nitrate reductase under low, more physiological concentrations of nadh. in this assay the reduction of nitrate is coupled to the oxidation of malate catalyzed by spinach nad-malate dehydrogenase. the use of this coupled system allows the assay of nitrate reductase activity at steady-state concentrations of nadh below micromolar. we have used this coupled assay to study the kinetic parameters of spinach nitrate reductase ... | 1990 | 16667335 |
| subcellular compartmentation of uridine nucleotides and nucleoside-5' -diphosphate kinase in leaves. | the subcellular compartmentation of nucleoside diphosphate kinase (ec 2.7.4.6) and the uridine nucleotides has been studied in leaves. membrane filtration of barley (hordeum vulgare l.) leaf mesophyll protoplasts and differential centrifugation of spinach (spinacia oleracea l.) leaf extracts showed that about half the nucleoside diphosphate kinase is present in the cytosol. the activity is adequate to account for the turnover of utp and udp during photosynthetic sucrose synthesis. nonaqueous den ... | 1990 | 16667327 |
| protective systems against active oxygen species in spinach: response to cold acclimation in excess light. | spinach (spinacia oleracea l.) plants were acclimated to 1° c or maintained at 18° c under the same light regime (260-300 μmol photons·m(-2)·s(-1)). the cold acclimation led to several metabolic and biochemical changes that apparently include improved protection of the photosynthetic apparatus against active oxygen species. in particular, cold-acclimated leaves exhibited a considerably higher ascorbate content and significantly increased activities of superoxide dismutase, ascorbate peroxidase, ... | 1990 | 24202017 |
| the ferredoxin-thioredoxin system of a green alga, chlamydomonas reinhardtii : identification and characterization of thioredoxins and ferredoxin-thioredoxin reductase components. | the components of the ferredoxin-thioredoxin (ft) system of chlamydomonas reinhardtii have been purified and characterized. the system resembled that of higher plants in consisting of a ferredoxin-thioredoxin reductase (ftr) and two types of thioredoxin, a single f and two m species, m1 and m2. the chlamydomonas m and f thioredoxins were antigenically similar to their higher-plant counterparts, but not to one another. the m thioredoxins were recognized by antibodies to both higher-plant m and ba ... | 1990 | 24202012 |
| freezing of isolated thylakoid membranes in complex media. v. inactivation and protection of electron transport reactions. | when chloroplast thylakoid membranes isolated from spinach leaves (spinacia oleracea l. cv. monatol) were frozen in media containing the predominant inorganic electrolytes of the chloroplast stroma, linear photosynthetic electron transport became progressively inhibited. after onset of freezing, both psii- and psi-mediated electron flow were inactivated almost to the same extent. prolonged storage of the membranes in the frozen state increased damage to psii relative to psi activity. under these ... | 1990 | 24420991 |
| reversible photoinhibition of unhardened and cold-acclimated spinach leaves at chilling temperatures. | the photoinhibition of photosynthesis at chilling temperatures was investigated in cold-acclimated and unhardened (acclimated to +18° c) spinach (spinacia oleracea l.) leaves. in unhardened leaves, reversible photoinhibition caused by exposure to moderate light at +4° c was based on reduced activity of photosystem (ps) ii. this is shown by determination of quantum yield and capacity of electron transport in thylakoids isolated subsequent to photoinhibition and recovery treatments. the activity o ... | 1990 | 24201942 |
| spinach chloroplastic carbonic anhydrase: nucleotide sequence analysis of cdna. | we have determined the nucleotide sequence of a cdna encoding spinach (spinacia oleracea) chloroplastic carbonic anhydrase (ca). the open reading frame encodes a protein consisting of a transit peptide and a mature ca protein with a predicted mass of 24, 116 daltons. this represents the first report of a nucleotide sequence of a plant ca. | 1990 | 16667262 |
| a novel role for light in the activation of ribulosebisphosphate carboxylase/oxygenase. | light stimulated the activation of ribulosebisphosphate carboxylase/oxygenase (rubisco) in a buffered lysed chloroplast system in the presence of saturating concentrations of atp. this indicates a role for light in the rubisco activase activation system in addition to the previously identified requirement for the synthesis of atp. rubisco activation was nearly as great at low irradiance (10 micromoles of photons per square meter per second) as at high irradiance (1000 micromoles of photons per s ... | 1990 | 16667230 |
| the ferredoxin-thioredoxin system of a green alga, chlamydomonas reinhardtii: identification and characterization of thioredoxins and ferredoxin-thioredoxin reductase components. | the components of the ferredoxin-thioredoxin (ft) system of chlamydomonas reinhardtii have been purified and characterized. the system resembled that of higher plants in consisting of a ferredoxin-thioredoxin reductase (ftr) and two types of thioredoxin, a single f and two m species, m1 and m2. the chlamydomonas m and f thioredoxins were antigenically similar to their higher-plant counterparts, but not to one another. the m thioredoxins were recognized by antibodies to both higher plant m and ba ... | 1990 | 11538175 |
| photosynthetic control, "energy-dependent" quenching of chlorophyll fluorescence and photophosphorylation under influence of tertiary amines. | the effects of the tertiary amines tetracaine, brucine and dibucaine on photophosphorylation and control of photosynthetic electron transport in isolated chloroplasts of spinacia oleracea were investigated. tertiary amines inhibited photophosphorylation while the related electron transport decreased to the rates, observed under non-phosphorylating conditions. light induced quenching of 9-aminoacridine fluorescence and uptake of (14)c-labelled methylamine in the thylakoid lumen declined in parall ... | 1989 | 24424746 |
| low co(2) prevents nitrate reduction in leaves. | the correlation between co(2) assimilation and nitrate reduction in detached spinach (spinacia oleracea l.) leaves was examined by measuring light-dependent changes in leaf nitrate levels in response to mild water stress and to artificially imposed co(2) deficiency. the level of extractable nitrate reductase (nr) activity was also measured. the results are: (a) in the light, detached turgid spinach leaves reduced nitrate stored in the vacuoles of mesophyll cells at rates between 3 and 10 micromo ... | 1989 | 16667163 |
| fluorescence microscopy and radiolabeling of c3 and c 4 chloroplasts using diisothiocyanatostilbene disulfonic acid as a marker for the phosphate translocator. | the usefulness of 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (dids) for in-situ studies of the chloroplast phosphate translocator was evaluated by fluorescence microscopy and radiolabeling of spinach (spinacia oleracea l.) (c3 plant) and maize (zea mays l.) (c4 plant) chloroplasts. in maize mesophyll and bundle-sheath chloroplasts and in spinach chloroplasts that were either intact, broken or swollen, dids fluorescence was only associated with the chloroplast envelope. intact chloroplast ... | 1989 | 24201512 |
| direct measurement of k channels in thylakoid membranes by incorporation of vesicles into planar lipid bilayers. | light-driven electron transfer reactions cause the active accumulation of protons inside thylakoids, yet at steady state the electrical potential difference across the thylakoid membrane is very small; therefore, there must be a flux of other ions to balance the charge that would otherwise be built up by the net movement of h(+). this paper presents direct measurements of ion movements through channels in the thylakoid membrane. these were made possible by fusing thylakoid vesicles from spinach ... | 1989 | 16667005 |
| effects of inorganic phosphate on the light dependent thylakoid energization of intact spinach chloroplasts. | the light dependent energization of the thylakoid membrane was analyzed in isolated intact spinach (spinacia oleracea l.) chloroplasts incubated with different concentrations of inorganic phosphate (pi). two independent methods were used: (a) the accumulation of [(14)c]5,5-dimethyl-2,4-oxazolidinedione and [(14)c] methylamine; (b) the energy dependent chlorophyll fluorescence quenching. the inhibition of co(2) fixation by superoptimal medium pi or by adding glyceraldehyde-an inhibitor of the cal ... | 1989 | 16667000 |
| protoplast volume:water potential relationship and bound water fraction in spinach leaves. | methods used to estimate the (nonosmotic) bound water fraction (bwf) (i.e. apoplast water) of spinach (spinacia oleracea l.) leaves were evaluated. studies using three different methods of pressure/volume (p/v) curve construction all resulted in a similar calculation of bwf; approximately 40%. the theoretically derived bwf, and the water potential (psi(w))/relative water content relationship established from p/v curves were used to establish the relationship between protoplast (i.e. symplast) vo ... | 1989 | 16666983 |
| fluxes of atmospheric hydrogen sulphide to plant shoots. | short-term exposure of maize, pumpkin, spinach and spruce to various atmospheric h2 s concentrations resulted in high h2 s fluxes to the shoots. in all species an almost linear relation was observed between flux and h2 s concentration up to around 0.3 μl -1 . at higher h2 s concentrations the flux reached a maximum, which was about 0.08, 0.04, 0.1 and 0.03 μmol g f. wt-1 h-1 for maize, pumpkin, spinach and spruce, respectively. the transpiration rate was not affected during h2 s exposure. up to ... | 1989 | 29265436 |
| cytosolic phosphofructokinase from spinach leaves : ii. affinity for mg and nucleoside phosphates. | cytosolic atp-phosphofructokinase (pfk) from spinach leaves (spinacia oleracea l.) was inhibited by submillimolar concentrations of free mg(2+). the free mg(2+) concentration required for 50% inhibition of pfk activity was 0.22 millimolar. inhibition by free mg(2+) was independent of the mgatp(2-) concentration. inorganic phosphate (pi) reduces the inhibition of pfk activity by mg(2+). free atp (atp(4-)) also inhibits pfk activity. for free atp the inhibition of pfk activity was dependent on the ... | 1989 | 16666958 |
| cytosolic phosphofructokinase from spinach leaves : i. purification, characteristics, and regulation. | cytosolic atp-dependent phosphofructokinase (pfk) from spinach leaves (spinacia oleracea l.) was enriched 2600-fold by (nh(4))(2)so(4) fractionation, deae anion exchange chromatography, blue sepharose cl-6b, and atp agarose type 3-affinity chromatography. the final preparation had a specific activity of 417 nkat per milligram protein and exhibited four bands between 50 and 70 kilodaltons following denaturing electrophoresis. only one band of atp- and fructose 6-phosphate (f-6-p)-dependent, pisti ... | 1989 | 16666957 |
| fructose 2,6-bisphosphate hydrolyzing enzymes in higher plants. | the phosphatases that hydrolyze fructose 2,6-bisphosphate in a crude spinach (spinacia oleracea l.) leaf extract were separated by chromatography on blue sepharose, into three fractions, referred to as phosphatases i, ii, and iii, which were further purified by various means. phosphatase i hydrolyzed fructose 2,6-bisphosphate, with a k(m) value of 30 micromolar, to a mixture of fructose 2-phosphate (90%) and fructose 6-phosphate (10%). it acted on a wide range of substrates and had a maximal act ... | 1989 | 16666884 |
| sources of carbon for export from spinach leaves throughout the day. | rates of net carbon exchange, export, starch, and sucrose synthesis were measured in leaves of spinach (spinacia oleracea l.) throughout a 14-hour period of sinusoidal light to determine the sources of carbon contributing to export. net carbon exchange rate closely followed light level, but export remained relatively constant throughout the day. in the morning when photosynthesis was low, starch degradation provided most of the carbon for export, while accumulated sucrose was exported during the ... | 1989 | 16666868 |
| inactive photosystem ii complexes in leaves : turnover rate and quantitation. | the flash-induced electrochromic shift, measured by the amplitude of the rapid absorbance increase at 518 nanometers (deltaa518), was used to determine the amount of charge separation within photosystems ii and i in spinach (spinacia oleracea l.) leaves. the recovery time of the reaction centers was determined by comparing the amplitudes of deltaa518 induced by two flashes separated by a variable time interval. the recovery of the deltaa518 on the second flash revealed that 20% of the reaction c ... | 1989 | 16666841 |
| aerobic and anaerobic respiration in the intact spinach chloroplast. | aerobic and anaerobic chloroplastic respiration was monitored by measuring (14)co(2) evolution from [(14)c]glucose in the darkened spinach (spinacia oleracea) chloroplast and by estimating the conversion of fructose 1,6-bisphosphate to glycerate 3-phosphate in the darkened spinach chloroplast in air with o(2) or in n(2) with nitrite or oxaloacetate as electron acceptors. the pathway of (14)co(2) evolution from labeled glucose in the absence and presence of the inhibitors iodoacetamide and glycol ... | 1989 | 16666823 |
| identification and partial characterization of the denaturation transition of the light harvesting complex ii of spinach chloroplast membranes. | differential scanning calorimetry was employed to investigate the structure of spinach (spinacia oleracea) chloroplast membranes. in a low ionic strength hepes-buffered medium, major calorimetric transitions were resolved at 42.5 degrees c. (a), 60.6 degrees c (b), 64.9 degrees c (c(1)), 69.6 degrees c (c(2)), 75.8 degrees c (d), 84.3 degrees c (e), and 88.9 degrees c (f). a lipid melting transition was also commonly seen at 17 degrees c in scans starting at lower temperatures. the d transition ... | 1989 | 16666798 |
| immunodetection of the ferredoxin-nadp oxidoreductase-binding protein complex in thylakoids of different higher plant species. | monospecific polyclonal antibodies against thylakoid ferredoxin-nadp(+) oxidoreductase and its binding protein from spinacia oleracea were used to detect the presence of these proteins in different higher plants, including c(3), c(4), and crassulacean acid metabolism species. a remarkable conservation of antigenic determinants in all the species analyzed was demonstrated for both the reductase and its binding protein. the association of these polypeptides in a complex was detected by immunopreci ... | 1989 | 16666777 |
| betaine aldehyde dehydrogenase from spinach leaves: purification, in vitro translation of the mrna, and regulation by salinity. | spinach (spinacia oleracea l.) leaves contain a nuclear-encoded chloroplastic betaine aldehyde dehydrogenase (ec 1.2.1.8) which is induced several-fold by salinization. betaine aldehyde dehydrogenase was purified 2400-fold to homogeneity with an overall yield of 14%. the procedure included fractional precipitation with ammonium sulfate, followed by ion-exchange, hydrophobic interaction, and hydroxyapatite chromatography in open columns, and ion-exchange and hydrophobic interaction chromatography ... | 1989 | 2712575 |
| chloride inhibition of spinach nitrate reductase. | initial rate studies of spinach (spinacia oleracea l.) nitrate reductase showed that nadh:nitrate reductase activity was ionic strength dependent with elevated ionic concentration resulting in inhibition. in contrast, nadh:ferricyanide reductase was markedly less ionic strength dependent. at ph 7.0, nadh:nitrate reductase activity exhibited changes in the v(max) and k(m) for no(3) (-) yielding v(max) values of 6.1 and 4.1 micromoles nadh per minute per nanomoles heme and k(m) values of 13 and 18 ... | 1989 | 16666771 |
| a cerulenin insensitive short chain 3-ketoacyl-acyl carrier protein synthase in spinacia oleracea leaves. | a cerulenin insensitive 3-ketoacyl-acyl carrier protein synthase has been assayed in extracts of spinach (spinacia oleracea) leaf. the enzyme was active in the 40 to 80% ammonium sulfate precipitate of whole leaf homogenates and catalyzed the synthesis of acetoacetyl-acyl carrier protein. this condensation reaction was five-fold faster than acetyl-coa:acyl carrier protein transacylase, and the initial rates of acyl-acyl carrier protein synthesis were independent of the presence of cerulenin. in ... | 1989 | 16666765 |
| senescence-induced, thylakoid-bound diisopropylfluorophosphate-binding protein in spinach : induction pattern, localization, and some properties. | changes in diisopropylfluorophosphate (dfp)-binding proteins during development and senescence of spinach (spinacia oleracea) leaves were followed using [(3)h]dfp and sodium dodecylsulfate-polyacrylamide gel electrophoresis-fluorography. experiments using a series of aging stages of leaves attached to plants and ones with detached leaves stored in the dark both showed that a protein of 38 kilodaltons was the only major dfp-binding protein in the membrane fraction and that its dfp-binding increas ... | 1989 | 16666760 |
| studies of protein-protein interaction using countercurrent distribution in aqueous two-phase systems. partition behaviour of six calvin-cycle enzymes from a crude spinach (spinacia oleracea) chloroplast extract. | the partition behaviour of six enzymes of the calvin cycle in extracts of chloroplasts from spinach (spinacia oleracea) between two aqueous phases has been studied by countercurrent distribution. the enzymes showed distribution patterns which indicate heterogeneity and the presence of two or three fractions of most of the enzymes. when two of the enzymes, phosphoglycerate kinase and fructose-bisphosphate aldolase, were partitioned in both purified and partially purified form, they behaved like h ... | 1989 | 2730589 |
| effect of sulphate on glutamate synthesis by intact spinach (spinacia oleracea) chloroplasts. | during the course of nh4+ (or no2-)-plus-alpha-oxoglutarate-dependent o2 evolution in spinach (spinacia oleracea) chloroplasts, glutamate was continuously excreted out of the chloroplasts. under these conditions, for each molecule of no2- or nh4+ which disappeared, one molecule of glutamate accumulated in the medium and the concentration of glutamate in the stroma space was maintained constant. so4(2-) (or so3(2-) behave as inhibitors of nh4+ incorporation into glutamate by intact chloroplasts. ... | 1989 | 2730585 |
| protein phosphorylation as a mechanism for regulation of spinach leaf sucrose-phosphate synthase activity. | studies were conducted to determine whether protein phosphorylation may be a mechanism for regulation of spinach (spinacia oleracea l.) leaf sucrose-phosphate synthase (sps), shown previously to be light-dark regulated by some type of covalent modification. radioactive phosphate was incorporated into the 120-kda subunit of sps during labeling of excised leaves with [32p]pi, as shown by immunoprecipitation and denaturing gel electrophoresis of the enzyme. conditions which activated the enzyme (il ... | 1989 | 2523212 |
| short-term water stress leads to a stimulation of sucrose synthesis by activating sucrose-phosphate synthase. | the aim of this work was to identify which aspects of photosynthetic metabolism respond most sensitively to leaf water deficit. spinach (spinacia oleracea l.) leaf discs were floated on sorbitol concentrations of increasing molarity and changes of the protoplast volume were estimated using [(14)c]sorbitol and (3)h2o penetration. detached leaves were also wilted until 10% of their fresh weight was lost. photosynthesis was studied at very high external co2 concentrations, to eliminate the effect o ... | 1989 | 24212496 |
| effect of light on the chloroplast division cycle and dna synthesis in cultured leaf discs of spinach. | the effects of light on both the division cycle of chloroplasts and the synthesis of chloroplast dna were investigated in cultured discs taken from the distal end of 2-centimeter spinach (spinacia oleracea) leaves. comparisons were made of discs cultured for a maximum of 4 days in a shaking liquid medium under continuous white light, darkness, and of discs cultured for 1 day in light following 3 days in darkness. in continuous white light the shortest generation time of chloroplasts observed in ... | 1989 | 16666681 |
| inhibition of chloroplastic respiration by osmotic dehydration. | the respiratory capacity of isolated spinach (spinacia oleracea l.) chloroplasts, measured as the rate of (14)co(2) evolved from the oxidative pentose phosphate cycle in darkened chloroplasts exogenously supplied with [(14)c]glucose, was progressively diminished by escalating osmotic dehydration with betaine or sorbitol. comparing the inhibitions of co(2) evolution generated by osmotic dehydration in chloroplasts given c-1 and c-6 labeled glucose, 54% and 84% respectively, indicates that osmotic ... | 1989 | 16666679 |
| comparison of acetate- and pyruvate-dependent fatty-acid synthesis by spinach chloroplasts. | in recent studies using intact chloroplasts of spinach (spinacia oleracea l.) to investigate the accumulation of acetyl-coa produced by the activity of either acetyl-coa synthetase (ec 6.2.1.1) or the pyruvate-dehydrogenase complex, this product was not detectable. these results in combination with new information on the physiological levels of acetate and pyruvate in spinach chloroplasts (h.-j. treede et al. 1986, z. naturforsch. 41 c, 733-740) prompted a reinvestigation of the incorporation of ... | 1989 | 24212436 |