| short term acclimation of spinach to high temperatures: effect on chlorophyll fluorescence at 293 and 77 kelvin in intact leaves. | using intact leaves of spinacia oleracea (l.), reversible temperature-induced changes in chlorophyll fluorescence emitted at room temperature and at 77k were studied. interpretation of fluorescence at 77k was largely facilitated by developing a new method to minimize reabsorption artifacts (;diluted leaf-powder'). leaves of plants grown at 15 to 20 degrees c were exposed for several hours to different temperatures. upon incubation at 35 degrees c in the dark or in the light, the following change ... | 1984 | 16663430 |
| spinach pyruvate kinase isoforms : partial purification and regulatory properties. | pyruvate kinase from spinach (spinacea oleracea l.) leaves consists of two isoforms, separable by blue agarose chromatography. both isoforms share similar ph profiles and substrate and alternate nucleotide k(m) values. in addition, both isoforms are inhibited by oxalate and atp and activated by amp. the isoforms differ in their response to three key metabolites; citrate, aspartate, and glutamate. the first isoform is similar to previously reported plant pyruvate kinases in its sensitivity to cit ... | 1984 | 16663425 |
| interference by ddt and cyclodiene types of insecticides with chloroplast-associated reactions. | the effects of ddt, some of its analogs, and selected cyclodiene insecticides on isolated spinach (spinacea oleracea l.) thylakoids were identified, characterized, and compared to responses induced by selected herbicides. except for endrin, the insecticides inhibited light-induced electron transport, altered chlorophyll fluorescence transients, and competitively displaced [14c]atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], a known photosystem ii inhibitor, from the membranes. ... | 1984 | 6697419 |
| nine introns with conserved boundary sequences in the euglena gracilis chloroplast ribulose-1,5-bisphosphate carboxylase gene. | the single, chloroplast encoded gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcl) from euglena gracilis is found to contain nine intervening sequences. the intervening sequences were identified by heteroduplex analysis between euglena rbcl and the non-intron-containing rbcl from spinacea oleracea, by electron microscopy of euglena rbcl dna-mrna hybrids, and by cloning, restriction endonuclease analysis, and partial dna sequencing. the identification, locus, and ... | 1984 | 6319030 |
| inhibited light activation of fructose and sedoheptulose bisphosphatase in spinach chloroplasts exposed to osmotic stress. | the light activation of fructose-1,6-bisphosphatase (ec 3.1.3.11) and sedoheptulose-1,7-bisphosphatase (ec 3.1.3.37) was inhibited in isolated intact spinach (spinacia oleracea l.) chloroplasts exposed to reduced osmotic potentials. decreases in the velocity and magnitude of light activation correlated with the overall reduction in co2 fixation rates. responses of osmotically stressed chloroplasts to both varying ph and exogeous dihydroxyacetone phosphate (dhap) or 3-phosphoglycerete (pga) were ... | 1984 | 24258369 |
| thylakoid membrane stability in drought-tolerant and drought-sensitive plants. | the stress stability of membranes from two drought-tolerant plants (craterostigma plantagineum andceterach officinarum) was compared with that of a drought-sensitive plant (spinacia oleracea) in model experiments. thylakoids from these plants were exposed to excessive sugar or salt concentrations or to freezing. all stresses caused loss of membrane function as indicated by the loss of cyclic photophosphorylation or the inability of the membranes to maintain a large proton gradient in the light. ... | 1984 | 24253553 |
| temperature dependence of energy-transducing functions and inhibitor sensitivity in chloroplasts. | a comparative analysis of the temperature dependence of energy-transducing reactions in spinach (spinacia oleracea) chloroplasts and their sensitivity for uncouplers and energy-transfer inhibitors at different temperatures is presented. arrhenius plots reveal two groups of transitions, around 19 degrees c and around 12 degrees c. activities that show transitions around 19 degrees c include linear electron flow from water to ferricyanide, its coupled photophosphorylation, the dark-release of the ... | 1984 | 16663374 |
| sugar-nucleotide precursors of arabinopyranosyl, arabinofuranosyl, and xylopyranosyl residues in spinach polysaccharides. | cultured spinach (spinacia oleracea l. cv monstrous viroflay) cells incorporated exogenous l-[(3)h]arabinose sequentially into beta-l-arabinopyranose-1-phosphate, uridine diphospho-beta-l-arabinopyranose, uridine diphospho-alpha-d-xylopyranose and (in some experiments) alpha-d-xylopyranose-1-phosphate. the amount of (3)h in each of these compounds reached a plateau after a few minutes, and could be rapidly chased with nonradioactive l-arabinose, demonstrating rapid turnover. after a few minutes' ... | 1983 | 16663328 |
| pyridine nucleotides and redox-charge evolution during the induction of flowering in spinach leaves. | in the long-day plant spinacia oleracea changes in the pool size of pyridine nucleotides have been followed under different photoperiodic conditions. in short days (vegetative state), the dark and light phases of the cycle are characterized by specific reciprocal changes in nad and nadp pool sizes. as a consequence, the ratios of nadh/nad+nadh and nadph/nadp+nadph, which are respectively considered to represent the catabolic and anabolic state of metabolism, also show a characteristic pattern. u ... | 1983 | 24258176 |
| far-red light-induced changes in intracellular potentials of spinach mesophyll cells: interaction with red light. | in green plants, the large bioelectric changes that photosynthetically active light stimulates make it difficult to observe electrical potential changes related to phytochrome photoconversion. as a first step towards distinguishing between photosynthetic and phytochrome effects, we showed that red light enhances far-red stimulated intracellular potential changes in spinach (spinacia oleracea) leaf mesophyll cells.for a dark-adapted leaf, the response to far-red light increased during the first 1 ... | 1983 | 16663280 |
| simultaneous measurement of oscillations in oxygen evolution and chlorophyll a fluorescence in leaf pieces. | in spinach (spinacia oleracea) and barley (hordeum vulgare) leaves, chlorophyll a fluorescence and o(2) evolution have been measured simultaneously following re-illumination after a dark interval or when steady state photosynthesis has been perturbed by changes in the gas phase. in high co(2) concentrations, both o(2) and fluorescence can display marked dampening oscillations that are antiparallel but slightly out of phase (a rise or fall in fluorescence anticipating a corresponding fall or rise ... | 1983 | 16663255 |
| a calcium-selective site in photosystem ii of spinach chloroplasts. | after acid-treatment of spinach (spinacia oleracea) chloroplasts, various partial electron transport reactions are inactivated from 25 to 75%. divalent cations in concentrations from 10 to 50 millimolar can partially restore electron transport rates. two cation-specific sites have been found in photosystem ii: one on the 3-(3,4-dichlorophenyl)-1, 1-dimethylurea-insensitive silicomolybdate pathway, which responds better to restoration by mg(2+) than by ca(2+) ions, the other on the forward pathwa ... | 1983 | 16663213 |
| photosynthesis and ion content of leaves and isolated chloroplasts of salt-stressed spinach. | spinach (spinacia oleracea) plants were subjected to salt stress by adding nacl to the nutrient solution in increments of 25 millimolar per day to a final concentration of 200 millimolar. plants were harvested 3 weeks after starting nacl treatment. fresh and dry weight of both shoots and roots was decreased more than 50% compared to control plants but the salt-stressed plants appeared healthy and were still actively growing. the salt-stressed plants had much thicker leaves. the salt-treated plan ... | 1983 | 16663201 |
| uptake of l-ascorbate by intact spinach chloroplasts. | uptake of l-[1-(14)c]ascorbate by intact ascorbate-free spinach (spinacia oleracea l. cv vital(r)) chloroplasts has been investigated using the technique of silicone oil filtering. rates greater than 100 micromoles per milligram chlorophyll per hour (external concentration, 10 millimolar) of ascorbate transport were observed. ascorbate uptake into the sorbitol-impermeable space (stroma) followed the michaelis-menten-type characteristic for substrate saturation. a k(m) of 18 to 40 millimolar was ... | 1983 | 16663182 |
| properties of the isolated intact chloroplast at cytoplasmic k concentrations : i. light-induced cation uptake into intact chloroplasts is driven by an electrical potential difference. | photosynthesis, stroma-ph, and internal k(+) and cl(-) concentrations of isolated intact chloroplasts from spinacia oleracea, as well as ion (k(+), h(+), cl(-)) movements across the envelope, were measured over a wide range of external kcl concentrations (1-100 millimolar).isolated intact chloroplasts are a donnan system which accumulates cations (k(+) or added tetraphenylphosphonium(+)) and excludes anions (cl(-)) at low ionic strength of the medium. the internally negative dark potential becom ... | 1983 | 16663169 |
| metabolism of glycolate and glyoxylate in intact spinach leaf peroxisomes. | intact and broken (osmotically disrupted) spinach (spinacia oleracea) leaf peroxisomes were compared for their enzymic activities on various metabolites in 0.25 molar sucrose solution. both intact and broken peroxisomes had similar glycolate-dependent o(2) uptake activity. in the conversion of glycolate to glycine in the presence of serine, intact peroxisomes had twice the activity of broken peroxisomes at low glycolate concentrations, and this difference was largely eliminated at saturating gly ... | 1983 | 16663164 |
| on the light dependence of fatty acid synthesis in spinach chloroplasts. | the capacity of intact chloroplasts to synthesize long chain fatty acids from acetate depends on the stroma ph in spinacia oleracea, u. s. hybrid 424. the ph optimum is close to 8.5. lowering of the stroma ph leads to a reduction of acetate incorporation but does not suffice to eliminate fatty acid synthesis completely. chain elongation from palmitic to oleic acid shows the same ph dependence. fatty acid synthesis is activated in the dark upon the simultaneous addition of dihydroxyacetone phosph ... | 1983 | 16663156 |
| molecular properties of 5-aminolevulinic acid dehydratase from spinacia oleracea. | 5-aminolevulinic acid dehydratase from spinach (spinacia oleracea), highly purified by immunoprecipitation, was characterized by inhibitor studies, amino acid composition, the mode of substrate binding and electron photomicrography. the results show that the conversion of 5-aminolevulinate to porphobilinogen requires an active arginine residue and the formation of a schiff base between the enzyme and 5-aminolevulinate. the formation of a schiff base is well known for bacterial and animal dehydra ... | 1983 | 6884359 |
| a role for fructose 2,6-bisphosphate in the regulation of sucrose synthesis in spinach leaves. | the subcellular distribution of fructose 2,6-bisphosphate in spinach (spinacia oleracea) leaves was studied using nonaqueous fractionation, showing that all, or almost all, is located in the cytosol. the amount of fructose 2,6-bisphosphate present in leaves during the diurnal cycle was measured and compared to the accumulation of starch and sucrose, and the amounts of selected phosphorylated intermediates in the leaf. upon illumination, the level of fructose 2,6-bisphosphate decreases, but prolo ... | 1983 | 16663136 |
| reduced osmotic potential inhibition of photosynthesis : site-specific effects of osmotically induced stromal acidification. | the effects of reduced reaction medium osmotic potential (0.67 molar sorbitol as compared to a control treatment with 0.33 molar sorbitol) on the enzymic steps of the photosynthetic carbon reduction cycle were investigated using isolated spinach (spinacia oleracea l. var longstanding bloomsdale) chloroplasts. reversal of reduced osmotic potential inhibition of photosynthetic rates by a stromal alkalating agent (nh(4)cl) was associated with specific steps of the cycle. low osmotic potential induc ... | 1983 | 16663127 |
| regulation of chloroplastic carbonic anhydrase : effect of magnesium. | it was previously reported that magnesium ion inhibited carbonic anhydrase (bamberger and avron 1975 plant physiol 56: 481-485). studies with partially purified carbonic anhydrase from spinach (spinacia oleracea l.) chloroplasts show that the effect was the result of the chloride counterion and not the magnesium ion. enzyme activity was reduced 50% upon addition of 3 to 10 millimolar mgcl(2) or kcl while all additions of mgso(4) between 0.3 and 10 millimolar were mildly stimulatory. | 1983 | 16663052 |
| molecular structure and subcellular localization of spinach leaf glycolate oxidase. | glycolate oxidase (e.c. 1.1.3.1) was purified from spinach leaves (spinacia oleracea). the molecular weight of the native protein was determined by sucrose density gradient centrifugation to be 290,000 daltons (13s), whereas that of the monomeric form was 37,000 daltons. the quaternary structure of the holoenzyme is likely to be octameric, analogous to pumpkin cotyledon glycolate oxidase [nishimura et al, 1982]. the subcellular localization of the enzyme was studied using linear sucrose density ... | 1983 | 24458446 |
| glyoxylate and glutamate effects on photosynthetic carbon metabolism in isolated chloroplasts and mesophyll cells of spinach. | addition of millimolar sodium glyoxylate to spinach (spinacia oleracea) chloroplasts was inhibitory to photosynthetic incorporation of (14)co(2) under conditions of both low (0.2 millimolar or air levels) and high (9 millimolar) co(2) concentrations. incorporation of (14)c into most metabolites decreased. labeling of 6-p-gluconate and fructose-1,6-bis-p increased. this suggested that glyoxylate inhibited photosynthetic carbon metabolism indirectly by decreasing the reducing potential of chloropl ... | 1983 | 16663018 |
| effects of glyoxylate on photosynthesis by intact chloroplasts. | because glyoxylate inhibits co(2) fixation by intact chloroplasts and purified ribulose bisphosphate carboxylase/oxygenase, glyoxylate might be expected to exert some regulatory effect on photosynthesis. however, ribulose bisphosphate carboxylase activity and activation in intact chloroplasts from spinacia oleracea l. leaves were not substantially inhibited by 10 millimolar glyoxylate. in the light, the ribulose bisphosphate pool decreased to half when 10 millimolar glyoxylate was present, where ... | 1983 | 16663017 |
| evidence for endogenous cyclic photophosphorylation in intact chloroplasts: co(2) fixation with dihydroxyacetone phosphate. | this study examines the capacity of intact spinach (spinacia oleracea l.) chloroplasts to fix (14)co(2) when supplied with benson-calvin cycle intermediates in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (dcmu). under these conditions, substantial (14)co(2) fixation occurred in the light but not in the dark when either dihydroxyacetone phosphate, ribulose 5-phosphate, fructose 6-phosphate, or fructose bisphosphate was added. the highest rate of (14)co(2) fixation (20-40 micromoles pe ... | 1983 | 16663000 |
| evidence for cyclic photophosphorylation during co(2) fixation in intact chloroplasts: studies with antimycin a, nitrite, and oxaloacetate. | this study examines the effect of antimycin a and nitrite on (14)co(2) fixation in intact chloroplasts isolated from spinach (spinacia oleracea l.) leaves. antimycin a (2 micromolar) strongly inhibited co(2) fixation but did not appear to inhibit or uncouple linear electron transport in intact chloroplasts. the addition of small quantities (40-100 micromolar) of nitrite or oxaloacetate, but not nh(4)cl, in the presence of antimycin a restored photosynthesis. antimycin a inhibition, and the subse ... | 1983 | 16662999 |
| effect of photoperiod on the metabolism of deuterium-labeled gibberellin a(53) in spinach. | application of gibberellin a(53) (ga(53)) to short-day (sd)-grown spinach (spinacia oleracea l.) plants caused an increase in petiole length and leaf angle similar to that found in plants transferred to long days (ld). [(2)h] ga(53) was fed to plants in sd, ld, and in a sd to ld transition experiment, and the metabolites were identified by gas chromatography with selected ion monitoring. after 2, 4, or 6 sd, [(2)h]ga(53) was converted to [(2)h]ga(19) and [(2)h]ga(44). no other metabolites were d ... | 1983 | 16662988 |
| reduced osmotic potential effects on photosynthesis : identification of stromal acidification as a mediating factor. | addition of sorbitol, which facilitated reductions in reaction medium osmotic potential from standard (0.33 molar sorbitol, -10 bars) isotonic conditions to a stress level of 0.67 molar sorbitol (-20 bars), inhibited the photosynthetic capacity of isolated spinach (spinacia oleracea) chloroplasts. this inhibition, which ranged from 64 to 74% under otherwise standard reaction conditions, was dependent on reaction medium inorganic phosphate concentration, with the phosphate optimum for photosynthe ... | 1983 | 16662927 |
| glutathione and ascorbic acid in spinach (spinacia oleracea) chloroplasts. the effect of hydrogen peroxide and of paraquat. | the stroma of spinach chloroplasts contains ascorbic acid and glutathione at millimolar concentrations. [reduced glutathione]/[oxidized glutathione] and [ascorbate]/[dehydroascorbate] ratios are high under both light and dark conditions and no evidence for a role of oxidized glutathione or dehydroascorbate in the dark-deactivation of fructose bisphosphatase could be obtained. addition of h2o2 to chloroplasts in the dark decreases the above ratios, an effect that is reversed on illumination. addi ... | 1983 | 6307273 |
| cryopreservation of spinach chloroplast membranes by low-molecular-weight carbohydrates. ii. discrimination between colligative and noncolligative protection. | thylakoid membranes isolated from spinach leaves (spinacia oleracea l. cv. monatol) were subjected to a freeze-thaw cycle in the presence of various concentrations of sugars, polyhydric alcohols, and nacl. functional integrity of the membranes was assayed by means of cyclic photophosphorylation. from the nonideal activity-concentration profiles of the carbohydrates the effective nacl concentrations in the surroundings of the membranes at the respective freezing temperatures were calculated. comp ... | 1983 | 6831914 |
| cryopreservation of spinach chloroplast membranes by low-molecular-weight carbohydrates. i. evidence for cryoprotection by a noncolligative-type mechanism. | in freezing experiments with isolated spinach thylakoids (spinacia oleracea l. cv. monatol) the cryoprotective efficiency of various low-molecular-weight polyols was determined. the activity of cyclic photophosphorylation was used as an assay for the functional integrity of the membranes. the results were compared with the osmotic behavior of the cryoprotectants at high concentrations. equimolal concentrations of polyols which exhibit nearly comparable freezing point depressions even at high con ... | 1983 | 6831913 |
| molecular structure and subcellular localization of spinach leaf glycolate oxidase. | glycolate oxidase (e.c. 1.1.3.1) was purified from spinach leaves (spinacia oleracea). the molecular weight of the native protein was determined by sucrose density gradient centrifugation to be 290,000 daltons (13s), whereas that of the monomeric form was 37,000 daltons. the quaternary structure of the holoenzyme is likely to be octameric, analogous to pumpkin cotyledon glycolate oxidase [nishimura et al, 1982]. the subcellular localization of the enzyme was studied using linear sucrose density ... | 1983 | 24458389 |
| effects of mannose on photosynthetic gas exchange in spinach leaf discs. | when mannose is provided in the transpiration stream to spinach (spinacia oleracea) leaf discs, a series of specific and nonspecific changes occur in co(2) and h(2)o vapor exchange as a function of feeding time. the initial increases in apparent photosynthesis and transpiration are nonspecific effects due to osmotic changes leading to passive stomatal opening. the mannose-specific effects are: (a) time-dependent changes in the co(2) concentration required for saturation; (b) complex kinetics of ... | 1983 | 16662766 |
| measurement of co(2) and h(2)o vapor exchange in spinach leaf discs : effects of orthophosphate. | a leaf chamber has been designed which allows the measurement of both co(2) and water vapor exchange in spinacia oleracea leaf discs. the center of the disc lies within a cylindrical gas chamber and its margins are enclosed within a cavity through which water or various metabolites can be pumped. in saturating light and normal atmospheres, the leaf discs have a relatively low resistance to h(2)o vapor transfer (r(w) = 1.87 seconds per centimeter) and can support high rates of photosynthesis for ... | 1983 | 16662765 |
| purification and characterization of beta-ketoacyl-acp synthetase i from spinacia oleracea leaves. | beta-ketoacyl-acyl carrier protein (acp) synthetase i was purified 180-fold from crude extracts of spinach leaves. the purified preparation was completely free from other component enzymes of the de novo fatty acid synthetase (fas) system. its molecular weight was estimated to be 56,000 by gel filtration. the apparent km value for malonyl-coa in the presence of acp and malonyl-coa:acp transacylase was 4 microm. purified synthetase i was highly active with acyl-acp having chain lengths from c2 to ... | 1983 | 6830245 |
| size heterogeneity in spinacia oleracea (spinach) chloroplast 5s ribosomal rna. | | 1982 | 7177851 |
| effect of osmotic stress on photosynthesis studied with the isolated spinach chloroplast : site-specific inhibition of the photosynthetic carbon reduction cycle. | the effects of reduced osmotic potential on the photosynthetic carbon reduction cycle were investigated by monitoring photosynthetic processes of spinach (spinacia oleracea l. var. long standing bloomsdale) chloroplasts exposed to increased assay medium sorbitol concentrations. co(2) assimilation was found to be inhibited at 0.67 molar sorbitol by about 60% from control rates at 0.33 molar sorbitol. this level of stress inhibition was greater than that affecting the reductive phase of the cycle; ... | 1982 | 16662712 |
| influence of light on the heat sensitivity of the photosynthetic apparatus in isolated spinach chloroplasts. | the most heat-sensitive functions of chloroplasts in spinacia oleracea l. including the stromal carboxylation reaction, the light-induced electrical field gradient across the thylakoid membrane, as well as the overall photosynthetic co(2) fixation were less affected by heat if chloroplasts were heated in the light: 50% inactivation occurred around 35 degrees c in the dark and around 40 degrees c in the light. relative low light intensities were sufficient to obtain optimal protection against hea ... | 1982 | 16662711 |
| evidence for the glutamine synthetase/glutamate synthase pathway during the photorespiratory nitrogen cycle in spinach leaves. | spinach leaf (spinacia oleracea l.) discs infiltrated with [(15)n]glycine were incubated at 25 degrees c in the light and in darkness for 0, 30, 60 and 90 minutes. the kinetics of (15)n-incorporation into glutamine, glutamate, asparagine, aspartate, and serine from [(15)n]glycine was determined. at the beginning of the experiment, just after infiltration (0 min incubation) serine, and the amido-n of glutamine and asparagine were the only compounds significantly labeled in both light- and dark-tr ... | 1982 | 16662707 |
| photoinhibition of co(2)-dependent o(2) evolution by intact chloroplasts isolated from spinach leaves. | intact spinach (spinacia oleracea l.) chloroplasts, when pre-illuminated at 4 millimoles quanta per square meter per second for 8 minutes in a co(2)-free buffer at 21% o(2), showed a decrease (30-70%) in co(2)-dependent o(2) evolution and (14)co(2) uptake. this photoinhibition was observed only when the o(2) concentration and the quantum fluence rate were higher than 4% and 1 millimole per square meter per second, respectively. there was only a small decrease in the extent of photoinhibition whe ... | 1982 | 16662672 |
| phosphatidylglycerol synthesis in spinach chloroplasts: characterization of the newly synthesized molecule. | intact chloroplasts from spinach (spinacia oleracea l., hybrid 424) readily incorporate [(14)c]glycerol-3-phosphate and [(14)c]acetate into diacylglycerol, monoacylglycerol, diacylglycrol, free fatty acids (only when acetate is the precursor), phosphatidic acid, phosphatidylcholine, and most notably phosphatidylglycerol. the fraction of phosphatidylglycerol synthesized is greatly increased by the presence of manganese chloride in the reaction mixture. glycerol-3-phosphate-labeled phosphatidylgly ... | 1982 | 16662664 |
| some properties of the chloroplast envelope as revealed by electrophoretic mobility studies of intact chloroplasts. | the electrophoretic mobility of mature spinach (spinacia oleracea l. var. americana) chloroplasts sampled over a 7-month period was between -2.03 and -2.45 micrometers per second per volt per centimeter when suspended in a solution containing 1 millimolar cacl(2). the surface charge density of edta-treated chloroplasts was calculated to be -7,400 electrostatic units per square centimeter representing, on the average, one electronic charge per 645 square angstroms. electrophoretic mobility increa ... | 1982 | 16662663 |
| hydrogen peroxide synthesis in isolated spinach chloroplast lamellae : an analysis of the mehler reaction in the presence of nadp reduction and atp formation. | light-dependent o(2) reduction concomitant with o(2) evolution, atp formation, and nadp reduction were determined in isolated spinach (spinacia oleracea l. var. america) chloroplast lamellae fortified with nadp and ferredoxin. these reactions were investigated in the presence or absence of catalase, providing a tool to estimate the reduction of o(2) to h(2)o(2) (mehler reaction) concomitant with nadp reduction. in the presence of 250 micromolar o(2), o(2) photoreduction, simultaneous with nadp p ... | 1982 | 16662662 |
| sulfite-induced lipid peroxidation in chloroplasts as determined by ethane production. | ethane formation, as a measure of lipid peroxidation, was studied in spinach (spinacia oleracea l.) chloroplasts exposed to sulfite. ethane formation required sulfite and light, and occurred with concomitant oxidation of sulfite to sulfate. in the dark, both ethane formation and sulfite oxidation were inhibited. ethane formation was stimulated by ferric or ferrous ions and inhibited by ethylenediamine tetraacetate. the photosynthetic electron transport modulators, 3-(3,4-dichlorophenyl)-1,1-dime ... | 1982 | 16662657 |
| chloroplast sulfhydryl groups and the light activation of fructose-1,6-bisphosphatase. | studies of isolated intact spinach (spinacia oleracea l.) chloroplasts reveal that most of the available sulfhydryl groups are associated with stromal protein as opposed to a thylakoid membrane fraction under non-denaturing conditions. increases in sulfhydryl content of approximately 50% occurred with illumination and could be correlated kinetically with a reductive activation of fructose-1,6-bisphosphatase during co(2)-assimilation. inhibition of linear electron flow with 3-(3,4-dichlorophenyl) ... | 1982 | 16662654 |
| photosynthetic oxygen exchange in isolated cells and chloroplasts of c(3) plants. | photosynthetic o(2)-production and photorespiratory o(2)-uptake were measured, using stable isotope techniques, in isolated intact leaf cells of the c(3) plant xanthium strumarium l., and isolated intact chloroplasts of spinacia oleracea l (var. yates 102). considerable light dependent o(2)-uptake was observed in both systems, a proportion of which could be suppressed by co(2) (63% suppression in chloroplasts by 50 micromolar co(2), 58% in cells by 100 micromolar co(2) and 250 micromolar o(2)). ... | 1982 | 16662645 |
| isolation of spinach leaf peroxisomes in 0.25 molar sucrose solution by percoll density gradient centrifugation. | a procedure for isolating spinach (spinacia oleracea l.) leaf peroxisomes in 0.25 molar sucrose solution by percoll density gradient centrifugation followed by removal of the percoll by washing and centrifugation was established. the preparation contains more than 90% peroxisomes as intact organelles with no detectable chlorophyll or cytochrome oxidase contamination. the peroxisomes are stable at 0 to 4 degrees c or 25 degrees c for at least 2 hours. | 1982 | 16662639 |
| effect of osmotic stress on photosynthesis studied with the isolated spinach chloroplast : generation and use of reducing power. | the effect of increasing assay medium sorbitol concentration from 0.33 to 1.0 molar on the photosynthetic reactions of intact and broken spinach (spinacia oleracea l. var. long standing bloomsdale) chloroplasts was investigated by monitoring o(2) evolution supported by the addition of glyceric acid 3-phosphate (pga), oxaloacetic acid (oaa), 2,5-dimethyl-p-benzoquinone, and 2,6-dichlorophenolindophenol or as o(2) uptake with methyl viologen as acceptor.uncoupled 2,6-dichlorophenolindophenol-suppo ... | 1982 | 16662629 |
| purification and characterizations of beta-ketoacyl-[acyl-carrier-protein] reductase, beta-hydroxyacyl-[acyl-carrier-protein] dehydrase, and enoyl-[acyl-carrier-protein] reductase from spinacia oleracea leaves. | | 1982 | 6756317 |
| modulation of chloroplast phosphofructokinase by nadph : a mechanism for linking light to the regulation of glycolysis. | phosphofructokinase has been partially purified from spinach (spinacia oleracea) chloroplasts and studied from the standpoint of light/dark regulation. at concentrations reported to occur physiologically, nadph effected a sharp inhibition of the enzyme by: (a) lowering its affinity (increasing the apparent k(m)) for both of its substrates, atp and fructose 6-phosphate; and (b) lowering its v(max). inhibition by nadph was independent of ph and was observed both at ph 7.9 (ph of chloroplast stroma ... | 1982 | 16662552 |
| 3-phosphoglycerate phosphatase activity in chloroplast preparations as a result of contamination by acid phosphatase. | the presence of a nonspecific acid phosphatase which had high activity with 3-phosphoglycerate as substrate has recently been reported in spinacia oleracea l. chloroplasts (mulligan, tolbert 1980 plant physiol 66: 1169-1173). the subcellular localization of this activity has been reinvestigated by differential centrifugation of spinach leaf homogenates. the fraction sedimenting at 1,200g comprised mostly intact chloroplasts and contained more than half the chlorophyll but only 5% of the 3-phosph ... | 1982 | 16662549 |
| effects of the relative extrachloroplastic concentrations of inorganic phosphate, 3-phosphoglycerate, and dihydroxyacetone phosphate on the rate of starch synthesis in isolated spinach chloroplasts. | the effect of external inorganic phosphate (pi) on starch synthesis in isolated spinach (spinacia oleracea american hybrid no. 424) chloroplasts in the presence of millimolar concentrations of 3-phosphoglycerate (pga) and/or dihydroxyacetone phosphate (dap) was examined. whereas co(2) fixation was relatively constant as the ratio of the external phosphate to the pga + dap varied from 1:3 to 3:1, starch synthesis varied from 17% to 2% of the co(2) fixation rate. with dap alone, maximal starch syn ... | 1982 | 16662502 |
| activation and deactivation of h-atpase in intact chloroplasts. | the light activation mechanism of the latent h(+)-atpase was investigated in intact spinach (spinacia oleracea, hybrid 424) chloroplasts. the following observations were made. (a) photosystem i electron acceptors such as methyl viologen, nitrite, oxaloacetate, etc., inhibit the light activation of the enzyme. (b) the electron transfer inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (dcmu) fully inhibits the process. (c) ascorbate plus diaminodurene or dithionite can restore light activation in ... | 1982 | 16662486 |
| effects of high-temperature stress on various biomembranes of leaf cells in situ and in vitro. | the sensitivity of photosynthetic and respiratory functions to supraoptimal temperature stress was compared after heating of leaves, protoplasts and membrane systems of spinach (spinacia oleracea l. cv. monatol) and lettuce (valerianella locusta [l.] betcke) in situ and in vitro.after heating of whole leaves or protoplasts, endogenous respiration was not or only slightly affected at temperatures which caused a marked decrease of photosynthesis. this was manifested when mitochondria and thylakoid ... | 1982 | 16662445 |
| the effects of high concentrations of salts on photosynthetic electron transport in spinach (spinacia oleracea) chloroplasts. | 1. photosynthetic electron transport from water to lipophilic photosystem ii acceptors was stimulated 3--5-fold by high concentrations (greater than or equal to 1 m) of salts containing anions such as citrate, succinate and phosphate that are high in the hofmeister series. 2. in trypsin-treated chloroplasts, k3fe(cn)6 reduction insensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea was strongly stimulated by high concentrations of potassium citrate, but there was much less stimulation of 2,6-dic ... | 1982 | 7126161 |
| visualization of a spinach plastid transcriptionally active dna-protein complex in a highly condensed structure. | a transcriptionally active dna-protein complex isolated from spinach spinacia oleracea plastids is visualized by electron microscopy in different conditions. this structure, after glutaraldehyde fixation, is highly condensed. dna is supertwisted with proteins bound to it producing a beaded substructure. when glutaraldehyde fixation is omitted this structure is less condensed and dna fibrils come out from a proteinous central body. the dna-protein complex can be separated into two populations by ... | 1982 | 16662371 |
| effects of glycine hydroxamate, carbon dioxide, and oxygen on photorespiratory carbon and nitrogen metabolism in spinach mesophyll cells. | the effects of added glycine hydroxamate on the photosynthetic incorporation of (14)co(2) into metabolites by isolated mesophyll cells of spinach (spinacia oleracea l.) was investigated under conditions favorable to photorespiratory (pr) metabolism (0.04% co(2) and 20% o(2)) and under conditions leading to nonphotorespiratory (npr) metabolism (0.2% co(2) and 2.7% o(2)). glycine hydroxamate (gh) is a competitive inhibitor of the photorespiratory conversion of glycine to serine, co(2) and nh(4) (+ ... | 1982 | 16662358 |
| studies on the reconstitution of o(2)-evolution of chloroplasts. | extraction of spinach (spinacia oleracea l.) chloroplasts with cholate-asolectin in the absence of mg(2+) results in the rapid and selective inactivation of o(2) evolution and a partial (30 to 40%) loss of photosystem ii (psii) donor activity without extraction of thylakoid bound mn ( approximately 5 to 6 mn per 400 chlorophyll). inclusion of ethylene glycol in the extractions inhibits loss of o(2) evolution and results in quantitative and qualitative differences in proteins solubilized but does ... | 1982 | 16662349 |
| inhibition of photosynthetic energy conversion by cupric ion : evidence for cu-coupling factor 1 interaction. | this study describes a specific cu(2+) and light-dependent inhibition of spinach (spinacia oleracea l.) chloroplast reactions involving coupling factor 1 function. a primary effect is an inhibition of photophosphorylation induced by illumination of class ii chloroplasts with micromolar cu(2+) and pyocyanine in the absence of adp, mg(2+), and hpo(4) (2-). the inhibition, which is dependent on free cu(2+) as indicated by protection by ethylene diamine tetraacetic acid and dithiothreitol, requires ... | 1982 | 16662341 |
| kinetic characterization of spinach leaf sucrose-phosphate synthase. | the spinach (spinacia oleracea) leaf sucrose-phosphate synthase was partially purified via deae-cellulose chromatography, and its kinetic properties were studied. fructose-6-phosphate saturation curves were sigmoidal, while udpglucose saturation curves were hyperbolic. at subsaturating concentrations of fructose-6-phosphate, 1,5 anhydroglucitol-6-phosphate had a stimulatory effect on enzyme activity, suggesting multiple and interacting fructose-6-phosphate sites on sucrose-phosphate synthase. th ... | 1982 | 16662338 |
| phenolic components of the primary cell wall. feruloylated disaccharides of d-galactose and l-arabinose from spinach polysaccharide. | 1. cell walls from rapidly growing cell suspension cultures of spinacia oleracea l. contained ferulic acid and p-coumaric acid esterified with a water-insoluble polymer. 2. prolonged treatment with trypsin did not release may feruloyl esters from dearabinofuranosylated cell walls, and the polymer was also insoluble in phenol/acetic acid/water (2:1:1, w/v/v). 3. treatment of the cell walls with the fungal hydrolase preparation "driselase' did liberate low-mr feruloyl esters. the major esters were ... | 1982 | 7115300 |
| calmodulin-dependent and independent nad kinase activities from cytoplasmic and chloroplastic fractions of spinach (spinacia oleracea l.). | nad kinase activity has been found in a soluble, cytoplasmic fraction and in the chloroplasts prepared from green spinach leaves. a small amount of both the cytoplasmic and the chloroplastic nad kinase activities was retained on a calmodulin-sepharose affinity column. the cytoplasmic nad kinase eluted from the affinity column was found to be enhanced by calmodulin in a ca(2+)-dependent manner. the chloroplastic enzyme which is located exclusively in the stroma and not in the envelope and thylako ... | 1982 | 24259024 |
| origin of acetate in spinach leaf cell. | mitochondria were isolated from spinach (spinacia oleracea l.) leaves using a percoll gradient step. the high purity of the organelle fraction is demonstrated by electron microscopy and biochemical parameters. in the matrix space of these mitochondria, a short-chain acyl-coenzyme a hydrolase is present that converts acetyl-coenzyme a to acetate and coenzyme a with reasonable rates (k(m), 150 micromolar; v(max), 140 nanomoles acetate formed milligram(1) protein hour(-1)). the enzyme is product in ... | 1982 | 16662316 |
| characterization of maltose biosynthesis from α-d-glucose-1-phosphate in spinacia oleracea. l. | the de novo synthesis of maltose in spinach (spinacia oleracea l.) was shown to be catalyzed by a maltose synthase, which converts two molecules of α-d-glucose-1-phosphate (α-g1p) (km 1.5 mmol l(-1)) to maltose and 2 orthophosphate (pi). this enzyme was purified 203-fold by fractionated ammonium sulfate precipitation and by column chromatography on sepharose 6b. the addition of α-g1p (15 mmol l(-1)) to the isolation buffer is required to stabilize the enzyme activity during the extraction and pu ... | 1982 | 24275923 |
| oxidation of nad(p)h in a reconstituted spinach chloroplast preparation using ascorbate and hydrogen peroxide. | the conversion of fructose-1,6-bisphosphate to glycerate-3-phosphate (pga) was studied in a reconstituted spinach (spinacia oleracea l.) chloroplast preparation to determine whether a chloroplast-localized nab(p)h-oxidizing system (kow, smyth, gibbs 1982 plant physiol 69: 72-76 with substrates of ascorbate, nad(p)h, and h(2)o(2) could serve as a coupling enzyme in the recycling of nad(p)h. the rate of pga formation was monitored as an indicator of nad(p) generation. with nad as a cofactor, ascor ... | 1982 | 16662286 |
| alteration in the acyl lipid composition of thylakoids induced by aging and its effect on thylakoid structure. | the alteration in both the lipid composition and chlorophyll proteins obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of detergent solubilized thylakoids was investigated on differentially aged spinach (spinacia oleracea l.) chloroplasts. freshly isolated material demonstrated seven major bands upon electrophoretic fractionation. membranes aged in vitro showed a diminution and/or a disappearance of some bands concomitant with changes in the acyl lipid composition of these m ... | 1982 | 16662242 |
| rapid correlation between the leaves of spinach and the photocontrol of a peroxidase activity. | the activity of a basic peroxidase extracted at high ph from spinach (spinacia oleracea) leaves is modified by an irradiation with 2-minute red light or 2-minute far red light. this fast response, apparently mediated by phytochrome, is also detected in other leaves darkened with black paper. it is proposed that some fast signal moves from irradiated to darkened leaves. this signal, but not the direct control of peroxidase activity in irradiated leaves, is suppressed by inhibitors known for their ... | 1982 | 16662225 |
| characterization of a photosynthesizing reconstituted spinach chloroplast preparation : regulation by primer, adenylates, ferredoxin, and pyridine nucleotides. | a particulate preparation (mgp) capable of photosynthetic co(2) assimilation without the addition of stromal protein was obtained by rupturing whole spinach (spinacia oleracea var. america) chloroplasts in 15 millimolar mgcl(2) buffered with tricine at ph 8.5. this co(2) assimilation was dependent upon light, inorganic phosphate, ferredoxin, adp, nad or nadp, and primer. excepting glycolate, the products of co(2) fixation by mgp were similar to those found with whole chloroplasts.glycerate-3-pho ... | 1982 | 16662154 |
| effects of magnesium on intact chloroplasts : ii. cation specificity and involvement of the envelope atpase in (sodium) potassium/proton exchange across the envelope. | addition of exogenous mg(2+) (2 millimolar) to illuminated intact spinach (spinacia oleracea l.) chloroplasts caused acidification of the stroma and a 20% decrease in stromal k(+). addition of k(+) (10-50 millimolar) reversed both stromal acidification and k(+) efflux from the chloroplast caused by mg(2+). these data suggested that mg(2+) induced reversible h(+)/k(+) fluxes across the chloroplast envelope. ca(2+) and mn(2+) (2 millimolar) were as effective as 4 millimolar mg(2+) in causing k(+) ... | 1981 | 16662089 |
| effects of freezing on spinach leaf mitochondria and thylakoids in situ and in vitro. | the sensitivity of spinach (spinacia oleracea l.) leaf mitochondria and chloroplast membranes to subzero temperature stress was compared after freezing of the membrane systems in situ and in vitro. respiratory and photosynthetic activities were measured polarographically.when leaves were frozen under controlled conditions for 2 hours to various minimum temperatures and mitochondria and chloroplasts isolated after thawing, the membrane systems showed a nearly simultaneous inactivation of respirat ... | 1981 | 16662067 |
| mechanism of glycolate transport in spinach leaf chloroplasts. | the incorporation of (14)co(2) into glycolate by intact spinach leaf (spinacia oleracea l. var. kyoho) chloroplasts exposed to (14)co(2) (nah(14)co(3), 1 millimolar) in the light was determined as a function of o(2) concentrations in the reaction media. a hyperbolic saturation curve was obtained, apparent k(m) (o(2)) of 0.28 millimolar, indicating that glycolate is produced predominantly by ribulose-1,5-bisphosphate carboxylase/oxygenase. a concentration gradient of glycolate was invariably obse ... | 1981 | 16662057 |
| restriction endonuclease cleavage site map of chloroplast dna from oenothera parviflora (euoenothera plastome iv). | 1) more than 50 cleavage sites produced by the restriction endonucleases sal i, pst i, kpn i, sma i and eco ri have been physically mapped on the 47 μm circular dna molecule of the euoenothera plastome iv. this plastome (= plastid genome) is considered to be the phylogenetically oldest of the subsection. 2) the dna molecule is segmentally organized into four regions represented by a large duplicated sequence in inverted orientation whose copies are separated by two single-copy segments. the sing ... | 1981 | 24276512 |
| photosynthesis of lipids from co(2) in spinacia oleracea. | young expanding spinach leaves exposed to (14)co(2) under physiological conditions for up to 20 minutes assimilated co(2) into lipids at a mean rate of 7.6 micromoles per milligram chlorophyll per hour following a lag period of 5 minutes. label entered into all parts of the lipid molecule and only 28% of the (14)c fixed into lipids was found in the fatty acid moieties, i.e. fatty acids were synthesized from co(2)in vivo at a mean rate of 2.1 micromoles per milligram chlorophyll per hour. intact ... | 1981 | 16661995 |
| activity of phosphatidylcholine-transfer protein from spinach (spinacia oleracea) leaves with mitochondria and chloroplasts. | a low-molecular-weight protein catalysing the transfer of phosphatidylcholine from liposomes to mitochondria and chloroplasts has been isolated from spinach (spinacia oleracea) by chromatography on sephadex g-75. | 1981 | 7325986 |
| diphenyl ether herbicides remarkably elevate the content in spinacia oleracea of (e)-3-(4-hydroxy-3-methoxyphenyl)-n-[2-(4-hydroxy-3-methoxyphenyl)ethyl]-2 propenamide. | | 2007 | 7310006 |
| amino acid synthesis in photosynthesizing spinach cells : effects of ammonia on pool sizes and rates of labeling from co(2). | isolated cells from leaves of spinacia oleracea have been maintained in a state capable of high rates of photosynthetic co(2) fixation for more than 60 hours. the incorporation of (14)co(2) under saturating co(2) conditions into carbohydrates, carboxylic acids, and amino acids, and the effect of ammonia on this incorporation have been studied. total incorporation, specific radioactivity, and pool size have been determined as a function of time for most of the protein amino acids and for gamma-am ... | 1981 | 16661904 |
| adenine nucleotides and energy charge evolution during the induction of flowering in spinach leaves. | changes in adenine nucleotides pool size levels have been investigated in spinach leaves (spinacia oleracea. l. cv. nobel) in order to characterize the transition from the vegetative to the reproductive development. the transient changes reported in this study are the earliest responses observed to date in leaves during photoperiodic induction. these results are discussed in relation to prigogine's theory of systems far from equilibrium. | 1981 | 24302414 |
| synthesis of phosphatidylglycerol by chloroplasts from leaves of spinacia oleracea l. (spinach). | | 1981 | 7294810 |
| compositional heterogeneity of the chloroplast dnas from euglena gracilis and spinacia oleracea. | the chloroplast genomes of euglena gracilis and spinacia oleracea were investigated in their compositional heterogeneity, by using different experimental approaches. euglena chloroplast dna has a dg + dc content of 28%. preparations averaging 20 x 10(6) in molecular weight exhibit a gross heterogeneity in their elution profiles from hydroxyapatite and in their buoyant densities because the rrna genes have a high rg + rc content. finer analysis by melting, buoyant density of restriction fragments ... | 1981 | 6791923 |
| subcellular localization of acetyl-coa synthetase in leaf protoplasts of spinacia oleracea. | | 1981 | 6117251 |
| an ultrastructural search for lectin-binding sites on surfaces of spinach leaf organelles. | organelles isolated from leaves of spinach (spinacia oleracea l.) were prefixed in glutaraldehyde and then incubated with ferritin conjugates of four lectins - concanavalin a (con a), ricinus communis l. agglutinin, mw 120,000 (rca), soybean agglutinin (sba), and wheat germ agglutinin (wga) - in order to probe their cytoplasmic surfaces for saccharide residues. in each case the major leaf organelles, including microbodies, mitochondria and chloroplast derivatives, failed to exhibit labeling when ... | 1981 | 24302382 |
| effects of cyanide on rates and products of fatty acid synthesis by chloroplasts isolated from spinacia oleracea. | cyanide inhibited unesterified fatty acid synthesis but stimulated glyceride synthesis from [1-(14)c]acetate when spinacia oleracea chloroplasts were incubated in basal media. both unesterified fatty acid and glyceride accumulation were inhibited when chloroplasts were incubated in a diacylglycerol mode. stimulation of chloroplast fatty acid synthesis by either exogenous coenzyme a or triton x-100 was almost completely abolished in the presence of cyanide. stearoyl-acp desaturation is considered ... | 1981 | 16661794 |
| freezing injury in cold-acclimated and unhardened spinach leaves : ii. effects of freezing on chlorophyll fluorescence and light scattering reactions. | leaves from cold-acclimated and from unhardened spinach plants (spinacia oleracea l.) were subjected to a freezing/thawing procedure in which varying minimum temperatures were reached. subsequently, the chlorophyll fluorescence induction signal (kautsky phenomenon) and the light-induced apparent absorbance changes at 535 nm (light-scattering changes indicative of the proton gradient, and absorbance changes induced by the membrane potential) of the leaves were studied to obtain information on the ... | 1981 | 24301977 |
| freezing injury in cold-acclimated and unhardened spinach leaves : i. photosynthetic reactions of thylakoids isolated from frost-damaged leaves. | spinach plants (spinacia oleracea l.) were frost-hardened by cold-acclimation to 1° c or kept in an unhardy state at 20°/14° c in phytotrons. detached leaves were exposed to temperatures below 0°c. rates of photosynthetic co2 uptake by the leaves, recorded after frost treatment, served as a measure of freezing injury. thylakoid membranes were isolated from frost-injured leaves and their photosynthetic activities tested. ice formation occurred at about-4° to-5° c, both in unhardened and cold-accl ... | 1981 | 24301976 |
| plant leaf alanine: 2-oxoglutarate aminotransferase. peroxisomal localization and identity with glutamate:glyoxylate aminotransferase. | the distribution of alanine:2-oxoglutarate aminotransferase (ec 2.6.1.2) in spinach (spinacia oleracea) leaf homogenates was examined by centrifugation in a sucrose density gradient. about 55% of the total homogenate activity was localized in the peroxisomes and the remainder in the soluble fraction. the peroxisomes contained a single form of alanine:2-oxoglutarate aminotransferase, and the soluble fraction contained two forms of the enzyme. both the peroxisomal enzyme and the soluble predominan ... | 1981 | 7306049 |
| calcium requirement for the secretion of peroxidases by plant cell suspensions. | spinach (spinacia oleracea, l.) cells in liquid culture release peroxidases. this release is reduced by egta and promoted by calcium ions. in a medium deprived of calcium the rate of peroxidase release is low, but immediately after addition of i mm calcium there is a sudden increase of the extracellular peroxidase activity. extracellular calcium apparently penetrates into the cultured cells rather freely and, as a consequence, the rate of peroxidase secretion by these cells is directly correlate ... | 1981 | 6792211 |
| the lack of a phospholipid-exchange-protein activity in soluble fractions of spinacia oleracea leaves. | when 14c-labelled liposomes prepared from spinacia oleracea leaf lipids or 14c-labelled microsomal fraction ('microsomes') prepared from spinacia oleracea leaf protoplasts were incubated with unlabelled intact chloroplasts, there was a considerable transfer of label to the chloroplasts. this transfer occurred in the absence of added protein, but was stimulated by soluble protein fractions from spinacia oleracea leaves. the stimulation was heat-stable and decreased after dialysis of the protein f ... | 1981 | 7305979 |
| the reactivation of nitrate reductase from spinach (spinacia oleracea l.) inactivated by nadh and cyanide, using trivalent manganese either generated by illuminated chloroplasts or as manganipyrophosphate. | nitrate reductase of spinach (spinacia oleracea l.) leaves which had been inactivated in vitro by treatment with nadh and cyanide, was reactivated by incubation with oxidant systems and measured as fmnh2-dependent activity. reactivation was produced with trivalent manganese compounds represented either by manganipyrophosphate or produced by oxidation of mn(2+) ions in the presence of illuminated chloroplasts and compared with reactivation obtained with ferricyanide. reactivation in the chloropla ... | 1980 | 24306689 |
| effects of ph and other factors on the phosphate dependence of photosynthesis in spinach chloroplasts. | chloroplast stromal volume and ph influenced the phosphate (pi)-dependence of photosynthesis of spinach (spinacia oleracea l.) chloroplasts. decreasing the sorbitol concentration in the reaction mixture from 0.35 to 0.25 m, or decreasing the external ph from 8.3 to 7.3, extended the induction period of photosynthesis and decreased both the optimal [pi] and the minimal [pi] required to inhibit o2 evolution completely. at least part of the effect of external ph was attributable to changes in strom ... | 1980 | 24306478 |
| studies on the kinetic mechanism of nitrate reductase from spinach (spinacea oleracea). | based on lineweaver-burk plots of the initial velocities, at different concentrations of nadh and nitrate, and product inhibition patterns, an iso ping pong bi bi steady state kinetic mechanism is proposed for the spinach nitrate reductase. this mechanism incorporates the concept that the oxidized enzyme is present in two isomeric forms. | 1980 | 7433751 |
| effect of hydrogen peroxide on spinach (spinacia oleracea) chloroplast fructose bisphosphatase. | thiol-treated spinach (spinacia oleracea) chloroplast fructose bisphosphatase (ec 3.1.3.11) is severely inhibited by h2o2, whereas the freshly purified enzyme is little affected. dithiothreitol reverses inhibition by h2o2, indicating that essential thiol groups are oxidized during h2o2 inactivation. a new role for the dithiol and thioredoxin systems that are operative in illuminated chloroplasts is proposed. | 1980 | 6257234 |
| action of calcium ions on spinach (spinacia oleracea) chloroplast fructose bisphosphatase and other enzymes of the calvin cycle. | thiol-treated spinach (spinacia oleracea) chloroplast fructose bisphosphatase is powerfully inhibited by ca2+ non-competitively with respect to its substrate, fructose 1,6-bisphosphate. 500 microm-ca2+ causes virtually complete inhibition and the ki is 40 microm. severe inhibition of sedoheptulose bisphosphatase is also caused by ca2+. a role for ca2+ in regulation of the calvin cycle in spinach chloroplasts is proposed. | 1980 | 6258561 |
| the role of chloroplasts and microsomal fractions in polar-lipid synthesis from [1-14c]acetate by cell-free preparations from spinach (spinacia oleracea) leaves. | 1. isolated spinach (spinacia oleracea) chloroplasts were incapable of accumulating polar lipids when incubated with [1-14c]acetate in a cofactor-free medium. when coa, atp and glycerol 3-phosphate were added to incubation media, the accumulated products were non-esterified fatty acids, acyl-coa and 1,2-diacylglycerol, all intermediates of lipid metabolism. 2. chloroplast acyl-coa was used to synthesize phosphatidylcholine only when a microsomal fraction was added back to the incubation medium. ... | 1980 | 7406878 |
| modulation of glucose-6-phosphate dehydrogenase by nadph, nadp(+) and dithiothreitol at variable nadph/nadp (+) ratios in an illuminated reconstituted spinach (spinacia oleracea l.) chloroplast system. | the light-dependent inhibition of glucose-6-phosphate dehydrogenase (ec 1.1.1.49), the key enzyme of the oxidative pentose phosphate cycle, can be gradually abolished in an illuminated reconstituted spinach chloroplast system by increasing the concentration of nadp(+). the inhibition caused by the effector which was produced by the system in the light is characterized as being of the competitive type with respect to nadp(+). the ki value is 0.070 mm. the addition of nadph to the illuminated reco ... | 1980 | 24311258 |
| construction of a sali/psti restriction map of spinach chloroplast dna using low-gelling-temperature-agarose electrophoresis. | the restriction endonucleases sali and psti cleave circular chloroplast dna of spinach (spinacia oleracea) into 12 and 10 fragments, respectively. the sum of the fragment sizes in each of the series is equivalent to the contour length of the molecule (about 95 md). a physical map was constructed by sequential digestions using low-gelling-temperature agarose to avoid the necessity of extracting the fragments from the gel. the circular dna molecule of spinach chloroplasts consists of two identical ... | 1980 | 6244211 |
| linoleate and alpha-linolenate synthesis by isolated spinach (spinacia oleracea) chloroplasts. | diacylgalactosylglycerol synthesis was a prerequisite for the incorporation of [1-14c]-acetate into linoleate and alpha-linolenate of isolated spinach (spinacia oleracea) chloroplasts. oleate at position 1 of diacylgalactosylglycerol was desaturated to linoleate and alpha-linolenate both in the light and in the dark. some desaturation of palmitate was also observed after prolonged incubations. | 1979 | 540049 |
| stoichiometry of carbon dioxide release and oxygen uptake during glycine oxidation in mitochondria isolated from spinach (spinacia oleracea) leaves. | mitochondria isolated from spinach (spinacia oleracea) leaves oxidized glycine with a stoichiometry of co2 evolution to o2 uptake of 2 : 1. in the absence of added substrate, the mitochondria exhibited an extremely low endogenous rate of o2 uptake. | 1979 | 534540 |
| on the mechanism of activation by light of the nadp-dependent malate dehydrogenase in spinach chloroplasts. | with intact spinach (spinacia oleracea l. cv. vital r) chloroplasts, the activity of the nadp-dependent malate dehydrogenase after activation by light was 30 micromoles of malate formed per milligram of chlorophyll per hour; an identical rate of o(2) evolution was obtained upon oxaloacetate reduction by the intact plastids. however, when the activity of nadp-dependent malate dehydrogenase was measured subsequently to maximal activation of the enzyme by dithiothreitol (dtt) an average rate of 113 ... | 1979 | 16661046 |
| intracellular localization of beta-aspartate kinase in spinach (spinacea oleracea). | | 1979 | 225209 |
| proline oxidase and water stress-induced proline accumulation in spinach leaves. | spinach (spinacia oleracea l.) leaf discs accumulated free proline when exposed to polyethylene glycol solutions of water potential less than -10 bars. at -20 bars, the accumulation was 11 micromoles per gram original fresh weight in a 24-hour period.when the leaf organelles were separated on a sucrose gradient, a proline oxidase was detected in the mitochondrial fraction. isolated mitochondria were used for the study of the properties of the enzyme which was assayed by both oxygen uptake measur ... | 1979 | 16660761 |