| bovine liver dihydrofolate reductase: purification and properties of the enzyme. | a purification procedure is reported for obtaining bovine liver dihydrofolate reductase in high yield and amounts of 100-200 mg. a key step in the procedure is the use of an affinity gel prepared by coupling pteroyl-l-lysine to sepharose. the purified reductase has a specific activity of about 100 units/mg and is homogeneous as judged by analytical ultracentrifugation, polyacrylamide gel electrophoresis, and titration with methotrexate. the products of the first step of edman degradation indicat ... | 1975 | 45 |
| purification and properties of escherichia coli dihydrofolate reductase. | dihydrofolate reductase has been purified 40-fold to apparent homogeneity from a trimethoprim-resistant strain of escherichia coli (rt 500) using a procedure that includes methotrexate affinity column chromatography. determinations of the molecular weight of the enzyme based on its amino acid composition, sedimentation velocity, and sodium dodecyl sulfate gel electrophoresis gave values of 17680, 17470 and 18300, respectively. an aggregated form of the enzyme with a low specific activity can be ... | 1975 | 46 |
| evidence of the involvement of a 50s ribosomal protein in several active sites. | the functional role of the bacillus stearothermophilus 50s ribosomal protein b-l3 (probably homologous to the escherichia coli protein l2) was examined by chemical modification. the complex b-l3-23s rna was photooxidized in the presence of rose bengal and the modified protein incorporated by reconstitution into 50s ribosomal subunits containing all other unmodified components. particles containing photooxidized b-l3 are defective in several functional assays, including (1) poly(u)-directed poly( ... | 1975 | 52 |
| hybrids of chemical derivatives of escherichia coli alkaline phosphatase. | the activities of hybrid dimers of alkaline phosphatase containing two chemically modified subunits have been investigated. one hybrid species was prepared by dissociation and reconstitution of a mixture of two variants produced by chemical modification of the native enzyme with succinic anhydride and tetranitromethane, respectively. the succinyl-nitrotyrosyl hybrid was separated from the other members of the hybrid set by deae-sephadex chromatography and then converted to a succinyl-aminotyrosy ... | 1975 | 86 |
| nitrofurazone-reducing enzymes in e. coli and their role in drug activation in vivo. | earlier work showed that escherichia coli contains at least two enzymes which reduce nitrofurazone and other nitrofuran derivatives. one of these enzymes is lacking in some nitrofurazone-resistant mutant strains. we now report that there are three separable nitrofuran reductases in this organism: reductase i (mol. wt. approximately 50 000, insensitive to o2), reductase iia (mol. wt. approximately 120 000, inhibited by oxygen), reductase iib (mol. wt. approximately 700 000, inhibited by o2). unst ... | 1975 | 136 |
| novel type of murein transglycosylase in escherichia coli. | the purification and properties of a novel type of murein transglycosylase from escherichia coli are described. the purified enzyme appears as a single band on sodium dodecyl sulfate-polyacrylamide gels and has an apparent molecular weight of approximately 65,000 as estimated by gel filtration and gel electrophoresis. it degrades pure murein sacculi from e. coli almost completely into low-molecular-weight products. the two prominent muropeptide fragments in the digest are the disaccharide-tripep ... | 1975 | 357 |
| phospholipase d activity of gram-negative bacteria. | a phospholipase hydrolyzing cardiolipin to phosphatidic acid and phosphatidyl glycerol was characterized in gram-negative bacteria but was absent in preparations of gram-positive bacteria, saccharomyces cerevisiae, and rat liver mitochondria. in cell-free extracts of escherichia coli, salmonella typhimurium, proteus vulgaris, and pseudomonase aeruginosa, this cardiolipin-hydrolyzing enzyme had similar ph and mg2+ requirements and displayed a specificity which excluded phosphatidyl glycerol and p ... | 1975 | 360 |
| expression of the hut operons of salmonella typhimurium in klebsiella aerogenes and in escherichia coli. | the normal hut (histidine utilization) operons, as well as those with mutations affecting the regulation of their expression, of salmonella typhimurium were introduced on an f' episome into cells of s. typhimurium and klebsiella aerogenes whose chromosomal hut genes had been deleted and into cells of escherichia coli, whose chromosome does not carry hut genes. the episomal hut operons respond in a manner very similar to induction and catabolite repression in all three organisms. the small differ ... | 1975 | 362 |
| sn-glycerol-3-phosphate acyltransferase activity in particulate preparations from anaerobic, light-grown cells of rhodopseudomonas spheroides. involvement of acyl thiolester derivatives of acyl carrier protein in the synthesis of complex lipids. | crude particulate preparations obtained from anaerobic, light-grown cells of rhodopseudomonas spheroides have been shown to possess a significant level of sn-glycerol-3-phosphate acyltransferase (ec 2.3.1.15) activity. in contrast to the enzyme from escherichia coli, the r. spheroides glycerophosphate acyltransferase has a high specificity for acyl thiolester derivatives of acyl carrier protein (acp) as acyl donors for the reaction. only limited , nonlinear glycerophosphate incorporation into li ... | 1975 | 387 |
| inhibitory effects of antihistamines and antiserotonins on the bone marrow reactions produced by escherichia coli endotoxin in mice. | the bone marrow reactions (that is, decrease of nucleated cell counts and increase of red blood cell counts) of mouse bone were observed 1 hr after injection of endotoxin and peaked after 18 hr. these reactions were significantly inhibited when diphenhydramine, promethazine (antihistamines), chlorpromazine (antiserotonin), or cyproheptadine (antihistamine and antiserotonin) was given 30 min before endotoxin. such bone marrow reactions were also induced with histamine or serotonin and peaked 1 hr ... | 1975 | 442 |
| effect of inorganic phosphate on acridine inhibition and plasmid curing in escherichia coli. | some mutants and stock strains of escherichia coli k12 were sensitive to acriflavine in the presence of inorganic phosphate but were resistant to acriflavine in its absence. they mutated spontaneously to resistance to acriflavine plus phosphate. the synergistic effect of phosphate on acriflavine sensitivity was increased at high ph values. genetic analysis suggested that the mutations occurred in the gene acra. electron microscopic observation suggested that the presence of acriflavine plus phos ... | 1975 | 466 |
| identification of the 30 s protein adjacent to peptidyl transferase catalytic center of escherichia coli ribosomes. | iodoacetylphenylalanyl-trnaphe was used as an affinity label to localize the ribosomal components involved in the peptidyl transferase catalytic center of escherichia coli ribosomes. when labeling was carried out at ph 5.0, the affinity label could specifically label the ribosomal components which comprise the catalytic center. analysis of ribosomal proteins which had reacted with the affinity label revealed that a 30 s subunit protein, s 20, was located at or near to the ribosomal binding site ... | 1975 | 611 |
| phix174 dna-dependent dna synthesis in vitro: requirement for p1 ban protein in dnab mutant extracts of escherichia coli. | ammonium sulfate fractionation of crude extracts of e. coli yields a soluble enzyme fraction (about 25-fold purification) that catalyzes the conversion of phix174 single-stranded dna to duplex dna. the reaction is rifampicin-resistant, requires single-stranded dna, mg++, deoxynucleoside triphosphates, and atp, and is stimulated by kcl. such soluble enzyme fractions were prepared from e. coli strains carrying the prophage mutant p1bac, in which the viral dnab analog (ban) protein is expressed con ... | 1975 | 670 |
| ubiquinone-mediated coupling of nadh dehydrogenase to active transport in membrane vesicles from escherichia coli. | addition of ubiquinone-1 to e. coli ml 308-225 membrane vesicles dramatically increases coupling between nadh oxidation and active transport such that initial rates and steady-state levels of lactose and amino-acid accumulation are comparable to those observed during d-lactate oxidation. similar but less dramatic effects are observed with the quinone and succinate or l-lactate. in the presence of nadh and ubiquinone-1, the vesicles also generate a membrane potential (interior negative) that is s ... | 1975 | 672 |
| the cathode bound group antigen of dysentery-provoking escherichieae (author's transl). | antigens from disrupted cells of dysentery-provoking and of non-enteropathogenic escherichieae were submitted to immunoelectrophoresis on cellulose acetate stripes at ph 8.0. among 6 immune sera produced for this purpose by immunizing rabbits against desintegrated dysentery bacteria, only one contained a precipitine reacting with an antigen similar to the "generic antigen" of belaya. this - at ph 8.0 - cathode-bound group antigen (kga) could not only be found in virulent but also in 5 attenuated ... | 1975 | 873 |
| aminoacylation of escherichia coli cysteine trna by selenocysteine. | | 1975 | 963 |
| microbiol growth in lipid emulsions used in parenteral nutrition. | parenteral nutrition via central venous catheterization is associated with serious risks, especially that of sepsis. lipid emulsion (intralipidsweden), which may be administered peripherally, was evaluated for its potential to support microbial growth. washed cultures of staphylococcus aureus, candida albicans, and three species of gram-negative rods were all capable of multiplying in the emulsion at room temperature. variations in inoculum size did not affect the growth rate. studies comparing ... | 1975 | 982 |
| dihydrofolate reductase from a methotrexate-resistant escherichia coli: proton magnetic resonance studies of complexes with folate and methotrexate. | | 1975 | 1012 |
| purification and some properties of a novel maltohexaose-producing exo-amylase from aerobacter aerogenes. | maltohexaose producing amylase (ec 3.2.1.-) is the fourth known exo-amylase, the three previously known being glucoamylase, beta-amylase and pseudomonas stutzeri maltotetraose producing amylase. the enzyme after release from aerobacter aerogenes cells by 0.1% sodium lauryl sulfate extraction was purified by ammonium sulfate precipitation, deae-sephadex column chromatography and sephadex g-100 gel filtration to 80-fold of the original sodium lauryl sulfate extract activity, it gave a single band ... | 1975 | 1094 |
| intermediate plateaux in kinetics of the reaction catalyzed by biodegradative l-threonine dehydratase from escherichia coli. | it has been shown that for the reaction catalyzed by "biodegradative" l-threonine dehydratase from e. coli strains k-12 and 980 in 0.5 m phosphate-carbonate buffer, ph 8.4 and ph 9.5, the plots of initial reaction rate (v) versus the initial substrate concentration (s0 are characterized by several inflection points, i. e. an intermediate plateau. the plot of v versus the allosteric activator (amp) concentration have very complicated shapes: there are several inflection points, and also the maxim ... | 1975 | 1111 |
| l-alphas, 5s-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (nsc-163501): a new amino acid antibiotic with the properties of an antagonist of l-glutamine. | l-alphas,5s-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (nsc-163501), an antibiotic elaborated by streptomyces sviceus, has been shown to be a powerful inhibitor of many mammalian and bacterial reactions involving the transfer of nitrogen from the gamma-carboxamide of l-glutamine. thus, the utilization of l-glutamine for the synthesis of carbamyl phosphate, l-asparagine, guanosine-5'-monophosphate, cytidine-5'-triphosphate, n-formylglycinamidine ribonucleotide, nad, glucosamine-6-pho ... | 1975 | 1147 |
| effect of ph and pyridoxal phosphate on the quaternary structure of e. coli glutamate decarboxylase. | | 1975 | 1215 |
| purification and properties of a periplasmic aminoendopeptidase from escherichia coli. | a periplasmic aminoendopeptidase from escherichia coli has been purified to hemogeneity. it is a monomer of molecular weight 45000 and containing one -- sh group that is necessary for catalytic activity. the study of its substrate specificity indicated that the enzyme has both aminopeptidase and endopeptidase activity. the ph optimum for l-alanine p-nitroanilide hydrolysis is between 7 and 7.5 and that for 125i-labeled casein proteolysis between 7.3 and 7.6. the activation energy for the hydroly ... | 1975 | 1271 |
| past and present aspects of diarrheal disease in childhood. clinical study and treatment (author's transl). | the etiologic and pathophysiologic findings described in the first part of this paper have important consequences: the recognition of the specific etiology of diarrhea requires new laboratory methods: most of these, however, are technically easy to perform and do not require a large laboratory. a long-ranging consequence of this changed concept is a well-founded modification of therapy. the most important discovery was, that in a well balanced glucose electrolyte solution sodium and glucose enha ... | 1975 | 1346 |
| microcalorimetric study of the anaerobic growth of escherichia coli: growth thermograms in a synthetic medium. | a microcalorimetric technique was used for studying the growth of escherichia coli during anaerobiosis. the growth thermograms obtained are complex and the shape of curves is dependent on the hydrogen lyase activity of the cells. fermentation balances are given for different culture conditions, and simple growth thermograms are obtained when the hydrogen lyase activity is inhibitied. | 1976 | 1371 |
| microcalorimetric study of the anaerobic growth of escherichia coli: measurements of the affinity of whole cells for various energy substrates. | microcalorimetry has been used to determine the affinity of whole cells of escherichia coli for glucose, galactose, fructose, and lactose. anaerobic growth thermograms were analyzed, and the km and vmax values for these energy substrates were measured at ph 7.8. results obtained with this technique using various organisms growing anaerobically on different sugars are compared. this comparison shows that in practically all cases the cellular rate of catabolic activity is a hyperbolic function of ... | 1976 | 1373 |
| purification and properties of beta-n-acetylglucosaminidase from escherichia coli. | beta-n-acetylglucosaminidase (ec 3.2.1.30) has been purified from escherichia coli k-12 to near homogeneity based on polyacrylamide gel electrophoresis in both 0.5% sodium dodecyl sulfate and in 6 m urea at ph 8.5. the purified enzyme shows a ph optimum of 7.7 and the km for p-nitrophenyl-beta-d-2-acetamido-2-deoxyglucopyranoside is 0.43 mm. the molecular weight of this enzyme, determined by both sephadex gel filtration and by sodium dodecyl sulfate gel electrophoresis, is equivalent to 36,000. ... | 1976 | 1377 |
| preparations and properties of ribonucleic acid polymerase from acinetobacter calcoaceticus. | deoxyribonucleic acid (dna)-dependent ribonucleic acid (rna) polymerase (ec 2.7.7.6) from acinetobacter calcoaceticus was purified to apparent homogeneity and its properties were compared with those of the escherichia coli b enzyme. the molecular weights of the two native active enzymes as well as their alpha and beta subunits appeared to be similar. no subunit corresponding to that of sigma from e. coli was found, and furthermore no separation between the beta subunits could be detected by gel ... | 1976 | 1380 |
| arginine decarboxylase from a pseudomonas species. | an arginine decarboxylase has been isolated from a pseudomonas species. the enzyme is constitutive and did not appear to be repressed by a variety of carbon sources. after an approximately 40-fold purification, the enzyme appeared more similar in its properties to the escherichia coli biosynthetic arginine decarboxylase than to the e. coli inducible (biodegradative) enzyme. the pseudomonas arginine decarboxylase exhibited a ph optimum of 8.1 and an absolute requirement of mg2+ and pyridoxal phos ... | 1976 | 1382 |
| derepression of certain aromatic amino acid biosynthetic enzymes of escherichia coli k-12 by growth in fe3+-deficient medium. | 3-deoxy-arabino-heptulosonic acid 7-phosphate synthase, prephenate dehydratase, tryptophan synthase, and 2,3-dihydroxybenzoylserine synthase enzyme activities are derepressed in wild-type escherichia coli k-12 cells grown on fe3+-deficient medium. this derepression is reversed when feso4 is added to the growth medium. addition of shikimic acid to the fe3+-deficient growth medium caused repression of the first three enzyme activities but not of 2,3-dihydroxybenzoylserine synthase activity. additi ... | 1976 | 1383 |
| purification to homogeneity and properties of two d-alanine carboxypeptidases i from escherichia coli. | three homogeneous preparations of d-alanine carboxypeptidases i have been obtained from escherichia coli strain h2143, termed enzymes ia, ib, and ic. enzyme ia purified from the membrane after extraction with triton x-100 appeared on sodium dodecyl sulfate gel electrophoresis to be a polypeptide doublet whose monomer molecular weights were about 32,000 and 34,000. in addition to d-alanine carboxypeptidase activity, it catalyzed a transpeptidase reaction with several substrates, bound 14cpenicill ... | 1976 | 1391 |
| inhibition of the antibacterial activity of gentamicin by urine. | urinary levels of antibiotics determine the outcome of treatment of most urinary tract infections. the antibacterial effect of gentamicin against escherichia coli and pseudomonas aeruginosa in urine was studied. with use of urinary constituents in concentrations normally found in human urine, it was shown that urine has an inhibitory effect that is dependent upon the acidity and total osmolality of the urine, as well as upon the presence of individual solutes. up to 40 times as much gentamicin m ... | 1976 | 1450 |
| kinetics and mechanisms of drug action on microorganisms xxii: effects of aminosidine with and without organism pretreatment with bacteriostatic agents. | escherichia coli generation in the logarithmic growth phase was inhibited in peptone broth usp at ph 7.0 without kill below 3.0 mug/ml of aminosidine. above this value, the logarithms of the number of viables of the drug-treated culture ultimately decreased linearly with time and the slopes of these plots were independent of concentration. a concentration-dependent lag in the time of attainment of the cidal action was observed, and the extent of this lag was related to the ease of emergence of r ... | 1975 | 1509 |
| high ph ammonia toxicity, and the search for life on the jovian planets. | jovian plants have enviroments apparently suitable for the evolution of life, but nevertheless, present severe challenges to organisms. one such challenge arises from the presence of ammonia. ammonia is an efficient biocide, its effect being dependent on ph as well as on concentration. the effects of ph and ammonia concentration were studied separately, where possible, on a variety of organisms, including some isolated from natural enviornments of high ph and/or ammonia concentration. escherichi ... | 1975 | 1698 |
| effect of different ph values on the activity and quaternary structure of asparaginase in escherichia coli extracts. | the effect of low ph values on the activity and stability of the quaternary structure of asparaginase from escherichia coli was investigated at early stages of purification of the enzyme. acidification of the e. coli extract was most effective before the biomass separation. this procedure helped to separate biomass together with coagulated ballast proteins and not to reduce the activity. upon storage of the acidified solution at 5 degrees c reversible dissociation of the tetrametric structure in ... | 1975 | 1737 |
| mechanistic studies of glutamine synthetase from escherichia coli: kinetic evidence for two reaction intermediates in biosynthetic reaction. | fast reaction techniques were used to study the kinetics of protein fluorescence intensity changes that are associated with the reactions of unadenylylated escherichia coli glutamine synthetase l-glutamate: ammonia ligase (adp-forming), ec 6.3.1.2 with its substrates. it was established that the synthesis of glutamine occurs by a stepwise mechanism. during the catalytic process two fluorometrically distinct intermediates were observed. both forward and reverse rate constants which lead to the fo ... | 1976 | 1758 |
| self-assembly of biological macromolecules. | the genetic apparatus of the cell is responsible for the accurate biosynthesis of the primary structure of macromolecules which then spontaneously fold up and, in certain circumstances, aggregate to yield the complex tertiary and quaternary structures of the biologically active molecules. structures capable of self-assembly in this range from simple monomers through oligomers to complex multimeric structures that may contain more than one type of polypeptide chain and components other than prote ... | 1975 | 1808 |
| immunological polyfunctionality of proteins and its meaning for the analysis of an allergen-active bacterial substrate. | it was shown with the aid of immunosorption of an allergen-active substrate of e. coli 020: k84 (no. 2-rii) that protein substances taking part in the phenomenon of cell hypersensitivity were active in the humoral immunity reactions. the allergenic and immunochemical activity served as functions of the same molecules of bacterial proteins, this substantiating the use of immunochemical analysis for the study of an allergen-active bacterial substrate. by protein denaturing it is possible to obtain ... | 1975 | 1948 |
| some properties of the alpha-hemolysin produced by a hemolytic strain of e. coli. | it was found that alpha-hemolysin of e. coli p 678 hiy+ was maximally active against human erythrocytes at ph 6.5. the hemolytic activity is characterized in time by a distinct lag-phase and a phase of the greatest velocity of the reaction immediately following it. the duration of the lag-phase and also the rate of hemolysis depends on alpha-hemolysin concentration, whose increase is accompanied by a decrease of the lag-phase and acceleration of hemolysis. there is a definite limit below which t ... | 1975 | 1949 |
| kinetics of a bacterial culture growth: validity of the affinity rule in biological systems. | the kinetic study of a process is usually performed by measuring a convenient intensive property, p, as a function of time. the "affinity rule" states that, when a given process takes place under different external constraints (e.g., different temperatures, pressures, ph values, etc.), the various p versus time curves are related by an affinity transformation parallel to the time axis: in other words the p versus log time curves are parallel and can be superimposed by translation. the validity o ... | 1975 | 2109 |
| the binding of reduced nicotinamide adenine dinucleotide to citrate synthase of escherichia coli k12. | citrate synthase from escherichia coli enhances the fluorescence of its allosteric inhibitor, nadh, and shifts the peak of emission of the coenzyme from 457 to 428 nm. these effects have been used to measure the binding of nadh to this enzyme under various conditions. the dissociation constant for the nadh-citrate synthase complex is about 0.28 mum at ph 6.2, but increases toward alkaline ph as if binding depends on protonation of a group with a pka of about 7.05. over the ph range 6.2-8.7, the ... | 1976 | 2277 |
| atpase of escherichia coli: purification, dissociation, and reconstitution of the active complex from the isolated subunits. | a simple procedure for the purification of mg2+-stimulated atpase of escherichia coli by fractionation with poly(ethylene glycols) and gel filtration is described. the enzyme restores atpase-linked reactions to membrane preparations lacking these activities. five different polypeptides (alpha, beta, gamma, delta, epsilon) are observed in sodium dodecyl sulfate electrophoresis. freezing in salt solutions splits the enzyme complex into subunits which do not possess any catalytic activity. the pres ... | 1976 | 2281 |
| biosynthesis of bacterial glycogen. purification and properties of the escherichia coli b adpglucose:1,4-alpha-d-glucan 4-alpha-glucosyltransferase. | the escherichia coli b glycogen synthase has been purified to apparent homogeneity with the use of a 4-aminobutyl-sepharose column. two fractions of the enzyme were obtained: glycogen synthase i with a specific activity of 380 mumol mg-1 and devoid of branching enzyme activity and glycogen synthase ii having a specific activity of 505 mumol mg-1 and containing branching enzyme activity which was 0.1% of the activity observed for the glycogen synthase. only one protein band was found in disc gel ... | 1976 | 2288 |
| conformations of lysine-sensitive aspartokinase. | 1. the technique of differential thermal and proteolytic inactivation has been employed as a conformational probe for the lysine-sensitive aspartokinase (ec 2.7.2.4) of escherichia coli b. 2. l-amino acid inhibitors of this enzyme each induce a characteristic enzyme conformation. this is evidenced by rates of thermal and proteolytic inactivation and arrhenius activation energies for thermal inactivation which are characteristic of the amino acid present. 3. phenylalanine and leucine binding are ... | 1976 | 2308 |
| purification, molecular multiplicity and kinetic properties of "biosynthetic" l-threonine dehydratase from e. coli k-12. | "biosynthetic" l-threonine dehydratase was purified to homogeneous state with yield 29% of total activity from e. coli k-12. the cells were disrupted by means of ultra sound. nucleic acids and nucleoproteins were precipitated with protamine sulphate, the proteins were fractioned with (nh4)2so4, by gel filtration through sephadex g-25 followed by chromatography on deae-cellulose using stepways elution by changing the ph-values. the homogenity of the enzyme was shown by polyacrylamide gel disc ele ... | 1975 | 2333 |
| the purification and properties of the trimethoprim-resistant dihydrofolate reductase mediated by the r-factor, r388. | the r-factor r388 mediates the production of a trimethoprim-resistant dihydrofolate reductase. this enzyme has a different molecular weight and ph profile to the trimethoprim-sensitive enzyme of the escherichia coli host. the r-factor mediated enzyme was separated completely from the host e. coli enzyme by deae-cellulose ion-exchange chromatography. the purified r-factor enzyme was about 20 000 times less susceptible to trimethoprim than the e. coli enzyme and although it was inhibited competiti ... | 1976 | 2472 |
| metallophosphoryl and apophosphoryl alkaline phosphatases. | the noncovalent phosphate (e-p) and covalent phosphory (e-p) complexes of zn(ii), cd(ii), and apoalkaline phosphatases of escherichia coli have been studied by stopped flow kinetic methods and 32p-labeling techniques. with 2,4-dinitrophenylphosphate as substrate, preincubation of the zn(ii) enzyme with pi at ph 8 slows the pre-steady state burst rate, but does not affect the burst magnitude of 1 mol of roh per enzyme dimer. preincubation of the enzyme with pi at ph 5.5 reduces the burst magnitud ... | 1976 | 2605 |
| 31p nmr of phosphate and phosphonate complexes of metalloalkaline phosphatases. | 31p nmr spectra of phosphate and phosphonate complexes of escherichia coli alkaline phosphatase have been obtained by fourier transform nmr methods. one equivalent of p1i, bound to zn(ii) alkaline phosphatase, ph 8, gives rise to a single 31p resonance 2 ppm downfield from that for pi, and assignable to the noncovalent complex, e-p. inorganic phosphate in excess of 1 eq per enzyme dimer gives rise to a resonance at the position expected for free pi. at ph 5.1, a second resonance appears 8.5 ppm ... | 1976 | 2606 |
| calcium transport driven by a proton gradient and inverted membrane vesicles of escherichia coli. | calcium transport into inverted vesicles of escherichia coli was observed to occur without an exogenous energy source when an artificial proton gradient was used. the orientation of the proton gradient was acid inside and alkaline outside. either phosphate or oxalate was necessary for transport, as was found for respiratory-driven or atp-driven uptake (tsuchiya, t., and rosen, b.p. (1975) j. biol. chem. 250, 7687-7692). phosphate accumulation was found to occur in conjunction with calcium accumu ... | 1976 | 2608 |
| proceedings: r-factor replication in an e. coli host with defective polymerase i. | | 1975 | 2720 |
| proceedings: optimal labelling of dna in thymineless escherichia coli. | | 1975 | 2721 |
| effect of a magnetic field on escherichia coli. | the decontaminating effect of the pulsing magnetic field on the e. coli infected reclaimed water was studied on two installations. the magnetic field intensity was 500 and 1000-1500 ersted and the microbial load was 1, 10 and 100 thous. microbial units per 1 ml. it was found that the magnetic treatment of water had a noticeable bactericidal effect. this indicated that the method can be used for decontamination of reclaimed water. | 1975 | 2806 |
| urine conservation by surface-active agents. | the antibacterial activity of surface-active substances -- catamine-ab, catapine b-300, giph-200 and tego-51 was measured on the e. coli and staphylococcus aureus cultures and anthracoid spores. the purpose of the measurements was to explore the use of the substances as urine conserving agents. catamine-ab showed the highest antibacterial activity. anthracoid spores exhibited the highest resistance to the substances; staphylococci were less resistant than e. coli. investigations of the effective ... | 1975 | 2807 |
| myocardial substrate utilization in anaphylactic shock. | changes in myocardial substrate utilization were studied in anesthetized dogs following the production of anaphylactic shock. mean arterial blood pressure, cardiac output, and ph decreased significantly during this form of shock. myocardial ffa oxidation was greatly diminished especially within the first hour following challenge and lactate uptake more than doubled during the same time. thus, it is concluded that myocardial substrate utilization shifted away from ffa and towards lactate during a ... | 1976 | 2930 |
| determination of the transferase activity of l-asparaginase. | a method for determination of the transferase activity of 1-asparaginase in presence of hydroxylamine is developed. the optimally determined quantity of the enzyme was from 0.7 to 20 i. u. the conditions optimal for the enzymatic reaction and for quantitative estimation of 1-aspartyl-beta-hydroxamic acid were studied. the transferase and hydrolase activities of 1-asparaginase from e. coli were compared. the enzyme catalyzed at equal rates hydrolysis and hydroxylaminolysis of 1-asparagine. | 1975 | 3024 |
| a method for the regulation of microbial population density during continuous culture at high growth rates. | a method for the continuous culture of microorganisms is described which employs growth-dependent ph changes to control the rate of addition of fresh medium to a culture vessel. the apparatus (the "phauxostat") supports, at constant ph, long-term continuous culture at rates near or at the maximum of which the organisms are capable. the buffering capacity of the inflowing medium determines the steady-state population density of the culture, but the rate of growth is independent of the buffering c ... | 1976 | 3144 |
| atp synthesis by an artificial proton gradient in right-side-out membrane vesicles of escherichia coli. | | 1976 | 3178 |
| manganese (ii) and substrate interaction with unadenylylated glutamine synthetase (escherichia coli w). ii. electron paramagnetic resonance and nuclear magnetic resonance studies of enzyme-bound manganese(ii) with substrates and a potential transition-state analogue, methionine sulfoximine. | the enhancement of the longitudinal proton relaxation rate of solvent water protons which occurs when mn(ii) is bound to the "tight" metal ion site of unadenylylated glutamine synthetase (gs) was used to determine the binding constant of l-methionine (sr)-sulfoximine to gs-mn(ii) complexes. the binary enhancement for gs-mn(ii) is 22 at 24 mhz, 25 degrees c. the enhancement is lowered in the presence of the sulfoximine and the computed dissociation constant is 30 mum with epsilont, the enhancemen ... | 1976 | 3200 |
| role of d-tryptophan oxidase in d-tryptophan utilization by escherichia coli. | mutants of escherichia coli k-12 that require l-tryptophan (trp) are normally unable to utilize d-tryptophan to fulfill their requirement. however, secondary mutations (dadr) that confer this ability can be isolated. in such strains two distinct enzymes are found to be produced at high levels: d-amino acid oxidase (ec 1.4.3.3) and d-tryptophan oxidase. a convenient assay procedure for d-tryptophan oxidase is described. the two enzymes could be distinguished on the basis of their sensitivity to i ... | 1976 | 3493 |
| transduction of chromosomal genes between enteric bacteria by bacteriophage p1. | we have used p1 transduction to create intergeneric hybrid strains of enteric bacteria by moving the gena and hut genes between klebsiella aerogenes, escherichia coli and salmonella typhimurium. the use of e. coli as the recipient in such transductions permits the construction of episomes and specialized transducing phage containing non-e. coli material. the effect of host restriction modification and deoxyribonucleic acid homology on the frequency of intergeneric transduction of these loci has ... | 1976 | 3494 |
| galactoside accumulation by escherichia coli, driven by a ph gradient. | acidification of the external medium results in thiomethylgalactoside accumulation in an energy-depleted adenosine triphosphatase-negative mutant of escherichia coli. | 1976 | 3495 |
| sulfate-reducing pathway in escherichia coli involving bound intermediates. | although a sulfate-reducing pathway in escherichia coli involving free sulfite and sulfide has been suggested, it is shown that, as in chlorella, a pathway involving bound intermediates is also present. e. coli extracts contained a sulfotransferase that transferred the sulfonyl group from a nucleosidephosphosulfate to an acceptor to form an organic thiosulfate. this enzyme was specific for adenosine 3'-phosphate 5'-phosphosulfate, did not utilize adenine 5'-phosphosulfate, and transferred to a c ... | 1976 | 3497 |
| an endonuclease from escherichia coli that introduces single polynucleotide chain scissions in ultraviolet-irradiated dna. | an endonuclease that makes single polynucleotide chain scissions in ultraviolet-irradiated dna has been purified from escherichia coli. the activity has the following properties: (a) unirradiated dna is attacked very little if at all; (b) single strand dna is not attacked, whether irradiated or not; (c) there is no requirement for divalent cations and the activity is not affected by the addition of edta; (d) the ph optimum is approximately 7; (e) the activity is inhibited by 1 m nacl, single str ... | 1976 | 3498 |
| a dacron wool packed-bed extracorporeal reactor: a kinetic study of immobilized escherichia coli ii l-asparaginase. | an extracorporeal reactor containing a packed bed of dacron fibers has been developed. escherichia coli ii l-asparaginase was coupled to the dacron using gamma-aminopropyltriethoxysilane and glutaraldehyde. the preparation had an activity of 37 iu per gram of dacron (37 degrees c). the apparent km was studied as a function of the flow rate. the data indicated that the apparent km approached the km of the native enzyme at flow rates of about 300 mg/min. in vivo use of l-asparaginase immobilized o ... | 1976 | 3508 |
| packing in a new crystalline form of glutamine synthetase from escherichia coli. | | 1976 | 3654 |
| conformational transitions of the lac repressor from escherichia coli. | | 1976 | 3656 |
| hemodynamic and respiratory responses of conscious swine to e. coli endotoxin. | the injection of a sublethal bolus of e. coli into conscious swine produces an early increase in pap and a decrease in lap. this hemodynamic effect may be secondary to the pulmonary venous constriction seen in other species, or may relate to demonstrated multiple pulmonary microemboli. hypoxemia developed in only four of 17 animals although all endotoxin-treated swine showed interstitial edema and elevated wet/dry weight ratios with normal pulmonary surfactant. in addition, endotoxin-treated swi ... | 1976 | 3664 |
| isoaccepting species of serine trna coded by bacteriophage t5sto. | by aminoacyl-trna-dna hybridization and chromatographic analysis, evidence was provided that the bacteriophage t5sto codes for two trnaser species. trinucleotide- or polynucleotide-stimulated binding experiments assigned the codons ucc or ucu to these two trnaser species. they also suggested that the synthesis of these two trnaser species does not modify the reading capacity for codons less used in escherichia coli f and corresponds to a different situation compared with the t4-coded trna's. | 1976 | 3665 |
| escherichia coli capsule bacteriophages. viii. fragments of bacteriophage 28-1. | as described previously, a host capsule depolymerase activity is associated with the particles of escherichia coli capsule bacteriophage 28-1. this is a large virus with a long, contractile tail terminating in a base plate with spikes. in the present work, isolated virions were exposed to a variety of dissociative reagents and conditions. they were then tested for residual infectivity and depolymerase activity, as well as inspected under an electron microscope. very mild acid treatment (10 to 15 ... | 1976 | 3668 |
| the state of energization of the membrane of escherichia coli as affected by physiological conditions and colicin k. | the bacterial protein colicin k, when added to sensitive escherichia coli in the presence of 3,3'-dihexyloxacarbocyanine, cuases a doubling in fluorescence of the probe. glucose and oxygen cause a decreased fluorescence while anoxia and cyanide cause a rise in fluorescence. these results in conjunction with the work of other laboratories suggest that colicin k causes a depolarization of the transmembrane electrical potential. fluorescence in the absence of colicin k was relatively independent of ... | 1976 | 4085 |
| fluorine-19 nuclear magnetic resonance study of fluorotyrosine alkaline phosphatase: the influence of zinc on protein structure and a conformational change induced by phosphate binding. | 19f nuclear magnetic resonance (nmr) spectroscopy has been used to study a fully active e. coli fluorotyrosine alkaline phosphatase. the fluorotyrosine resonances provide sensitive probes of the conformational states of the protein. they were used to follow the addition of zinc or cobalt to the apoprotein, and the titration of the protein with inorganic phosphate or the inhibitor 2-hydroxy-5-nitrobenzylphosphonate. the results indicate that 2 molecules of inorganic phosphate per dimer of alkalin ... | 1976 | 4091 |
| glutamine synthetase adenylyltransferase from escherichia coli: purification and physical and chemical properties. | the glutamine synthetase adenylyltransferase (ec 2.7.7.42), which catalyzes the adenylylation and deadenylylation of glutamine synthetase in e. coli, has been stabilized and purified 2200-fold to apparent homogeneity. sedimentation and electrophoresis studies show that the native enzyme is a single polypeptide chain of 115,000 +/- 5000 molecular weight with an isoelectric ph (pl) of 4.98, a sedimentation coefficient (s20.w0) of 5.6s, and a molar frictional coefficient (f/f0) of 1.52. an alpha-he ... | 1976 | 4094 |
| transfer rna methyltransferase activity in paramecium aurelia. | the trna methyltransferases from paramecium aurelia were investigated. the effects of varying the mg2+ and nh4+ concentrations, ph, and temperature on the methylation of escherichia coli b trna using extracts from p. aurelia were determined. optimum trna methyltransferase activity was observed at ph 7.8 and 37 degrees c. the mg2+ optimum occurred at 0.66 mm in the absence of nh4+ while the nh4+ optimum occurred at 100 mm in the absence of mg2+. analysis of the bases methylated in (e. coli b) trn ... | 1976 | 4103 |
| the threonine-sensitive homoserine dehydrogenase and aspartokinase activities of escherichia coli k-12. incubation of the enzyme in alkaline conditions: dissociation and disulfide-bridge formation. | aspartokinase i - homoserine dehydrogenase i from escherichia coli k-12, a homotetrameric enzyme, dissociates into dimers upon alkaline treatment. both aspartokinase and homoserine dehydrogenase inactivation, as well as desensitazion towards l-threonine, occur in a multi-step process. dithiothreitol stabilizes a dimeric form retaining full activity and sensitivity; l-homoserine stabilizing another dimeric form devoid of aspartokinase activity and retaining a substantial dehydrogenase activity in ... | 1976 | 4302 |
| ornithine carbamoyltransferase from escherichia coli w. purification, structure and steady-state kinetic analysis. | ornithine carbamoyltransferase from escherichia coli w was purified to homogeneity. the enzyme has a molecular weight of 105000. it is composed of three apparently identical subunits with molecular weights of 35000. the mechanism of the ornithine carbamoyltransferase enzyme system from e. coli w was investigated kinetically by using the approach of product inhibition and dead-end inhibition of both forward and reverse reactions. on the basis of the kinetic data and binding studies it appears tha ... | 1976 | 4319 |
| the proton electrochemical gradient in escherichia coli cells. | the internal ph of escherichia coli cells was estimated from the distribution of either 5,5-14cdimethyl-2,4-oxazolidinedione or 14cmethylamine. edta/valinomycin treatment of cells was employed to estimate delta psi from 86rb+ distribution concomitant with the delta ph for calculation of delta muh. respiring intact cells maintained an internal ph more alkaline by 0.63-0.75 unit than that of the milieu at extracellular ph 7, both in growth medium and kcl solutions. the delta ph decreased when resp ... | 1976 | 4325 |
| cephacetrile, a new cephalosporin: in vitro, pharmacological and clinical evaluation. | cephacetrile, a parenteral cephalosporin, was evaluated for in vitro antibacterial activity, clinical pharmacology and effectiveness in the treatment of severe infections. the antibacterial activity against 187 isolates was determined by an agar-dilution technique. the mics were 0.06 to 0.5 mug/ml for group a streptococcus, d. pneumoniae, and staph. aureus, 4-6 mug/ml for e. coli and klebsiella-enterobacter 8-32 mug/ml for pr. mirabilis and more than 500 mug/ml for ps. aeruginosa. a few strains ... | 1975 | 4377 |
| protonmotive force as the source of energy for adenosine 5'-triphosphate synthesis in escherichia coli. | net synthesis of adenosine 5'-triphosphate (atp) in energy-depleted cells of escherichia coli was observed when an inwardly directed protonmotive force was artificially imposed. in wild-type cells, atp synthesis occurred whether the protonmotive force was dominated by the membrane potential (negative inside) or the ph gradient (alkaline inside). formation of atp did not occur unless the protonmotive force exceeded a value of 200 mv. under these conditions, no atp synthesis was found when cells w ... | 1976 | 4427 |
| effect of colicin k on a membrane-associated, energy-linked function. | the purpose of this work was in investigate the capability of cell extracts of escherichia coli and e. coli treated with colicin k to catalyze the following energy-dependent reverse transhydrogenase reaction: nadp + nadh + atp in equilibrium nadph + nad +adp + pi. under anaerobic conditions this reaction requires the presence of a specific portion of the electron transport chain, a functional energy coupling system, including an adenosine triphosphatase, enzyme, and atp as energy source. the atp ... | 1976 | 4429 |
| 5' leads to 3'-exonucleases of bacteriophage t4. | two enzyme activities which release nucleotides preferentially from the 5' termini of dna were found in t4-infected escherichia coli. since no corresponding activities were found in uninfected cells, the activities appeared to be induced by t4. both activities are capable of excising pyrimidine dimers from ultraviolet-irradiated dna which has been treated with t4 endonuclease v. one of the activities , referred to as t4 exonuclease b, was purified 400-fold from an extract of t4v 1- infected cell ... | 1976 | 4453 |
| cation transport in escherichia coli. viii. potassium transport mutants. | analysis of k transport mutants indicates the existence of four separate k uptake systems in escherichia coli k-12. a high affinity system called kdp has a km of 2 mum, and vmax at 37 degrees c of 150 mumol/g min. this system is repressed by growth in high concentrations of k. two constitutive systems, trka and trkd, have km's of 1.5 and 0.5 mm and vmax's of 550 and 40 at 37 and 30 degrees c, respectively. mutants lacking all three of these saturable systems take up k slowly by a process, called ... | 1976 | 4578 |
| studies of introital colonization in women with recurrent urinary infections. v. the inhibitory activity of normal vaginal fluid on proteus mirabilis and pseudomonas aeruginosa. | normal vaginal fluid from premenopausal volunteers was inoculated with 10 strains of proteus mirabilis and 14 strains of pseudomonas aeruginosa at ph's of 4.3, 4.6 and 4.9. all bacteria were killed at ph 4.3. nine of 10 strains of proteus mirabilis and 12 of 14 pseudomonas aeruginosa were killed at ph 4.6. only 4 of 14 strains of pseudomonas aeruginosa were killed at ph 4.9, while 8 of 10 strains of proteus mirabilis were killed at the same ph. we conclude that in comparison to the common 0 grou ... | 1976 | 4631 |
| mechanistic studies of glutamine synthetase from escherichia coli: kinetics of adp and orthophosphate binding to the unadenylylated enzyme. | the kinetics of protein fluorescence change exhibited by adp or orthophosphate addition to the mg2+-or mn2+-activated unadenylylated glutamine synthetase from escherichia coli were studied. the kinetic patterns of these reactions are incompatible with a simple bimolecular binding process and a mechanism which required protein isomerization prior to substrate binding. they are consistent with a mechanism in which direct substrate binding is followed by a substrate-induced conformational change st ... | 1976 | 5113 |
| a quantitation of the factors which affect the hydrolase and transgalactosylase activities of beta-galactosidase (e. coli) on lactose. | a study was implemented to quantitate the hydrolase and transgalactosylase activities of beta-galactosidase (e. coli) with lactose as the substrate and to investigate various factors which affect these activities. at low lactose concentrations the rate of galactose production was equal to the rate of glucose production. the rate of galactose production relative to glucose, however, dropped dramatically at lactose concentrations higher than 0.05 m and production of trisaccharides and tetrasacchar ... | 1976 | 5122 |
| net synthesis of short rna chains by e. coli rna polymerase at low ph. | | 1975 | 5304 |
| nonspecific bactericidal activity of the lactoperoxidases-thiocyanate-hydrogen peroxide system of milk against escherichia coli and some gram-negative pathogens. | two strains of escherichia coli and one strain each of salmonella typhimurium and pseudomonas aeruginosa were killed by the bactericidal activity of the lactoperoxidase-thiocyanate-hydrogen peroxide system in milk and in a synthetic medium. h2o2 was supplied exogenously by glucose oxidase, and glucose was produced at a level which was itself noninhibitory. two phases were distinguished: the first phase was dependent on the oxidation of scn(-) by lactoperoxidase and h2o2, which was reversed by re ... | 1976 | 5374 |
| partial purification and properties of enterobacter cloacae heat-stable enterotoxin. | cell free preparations of the whole-cell lysate and ultrafiltration (uf) fractions of broth cultures of a strain of enterobacter cloacae, isolated from a puerto rican with tropical sprue, were assayed for their ability to induce in vivo net water secretion in the rat jejunum. the whole-cell lysate and um-10 retentate of broth cultures were inactive. the um-2 retentate and filtrate were active at a concentration of 100 mug/ml or more; the toxigenic activity was entirely retained, and increased to ... | 1976 | 5376 |
| acetyl coenzyme a carbosylase. circular dichroism studies of escherichia coli biotin carboxyl carrier protein. | the biotin carboxyl carrier protein (bccp) component of escherichia coli acetyl coenzyme a carboxylase and three peptides derived from bccp by proteolytic digestion have been examined by circular dichroism spectroscopy. bccp, which has a peptide molecular weight of 22,500, has a spectrum typical of globular proteins with negative extrema at 222 nm and 208 nm. the two smallest peptides, bccp(sc) and bccp(9,100), with molecular weights of 8,900 and 9,100, respectively, exhibit unusual positive cd ... | 1976 | 5438 |
| bacterial interference as a factor in renal infection. | these experiments have investigated the role of bacterial interference as a determinant in the epidemiology of renal infection. two unrelated strains of escherichia coli, e. coli 08 and 075, isolated from cases of clinical pyelonephritis were used. although both strains had identical morphology on conventional media they could be differentiated using genetically stable markers for streptomycin resistance and arabinose utilization. when the 2 strains of e. coli were introduced into the kidney sim ... | 1976 | 5564 |
| gentamicin-susceptibility of various pathogens isolated from clinical materials. | we studied on the antibacterial activity of gentamicin against various pathogens isolated from clinical materials mainly isolated during 1974 and 1975, comparing with other antibiotics. beta hemolytic streptococci, pneumococci and enterococci are less susceptible to gentamicin than staphylococci. staph, aureus and staph. epidermidis resistant to various antibiotics are very susceptible to gentamicin, and no resistant strain to this drug was found. haemophilus influenzae, h. parainfluenzae and h. ... | 1976 | 5619 |
| preparation and properties of poly 2'-o-ethylcytidylic acid. | poly 2'0-ethylcytidylic acid (poly (ce)) was prepared by polymerization of 2'-0-ethylcytidine-5'-pyrophosphate with escherichia coli polynucleotide phosphorylase in the presence of mn++, and its properties compared with those of poly (rc), poly (cm) and poly (dc). the neutral form of poly (ce) exhibits properties similar to those of poly (rc) and poly (cm). it also forms an acid twin-stranded helix with a transition ph of 5.9 in 0.1 m nacl. the neutral form readily forms a double-stranded helica ... | 1976 | 5710 |
| bacteriophage t5-induced endonucleases that introduce site-specific single-chain interruptions in duplex dna. | four site-specific endodeoxyribonucleases have been partially purified from extracts of bacteriophage t5-infected escherichia coli by gel filtration and affinity chromatography on single- and double-stranded dna. the enzymes were detected and characterized by agarose gel electrophoresis of alkali-denatured digestion products. none of the four is found in uninfected cells. in the presence of a divalent cation, all four endonucleases make ligase-repairable, single-chain interruptions at specific s ... | 1976 | 5725 |
| myocardial function and energetics during acute escherichia coli endotoxin administration: in vivo and in vitro investigations. | | 1975 | 5758 |
| bacteriological examinations of bronchial secretion in children with non-specific bronchopulmonary disease (author's transl). | one thousand specimens of bronchial secretion from children with non-specific respiratory diseases have been examined bacteriologically. in spite of the complex nature of acute and especially of chronic respiratory disease the role of bacterial infection should not be underestimated. thirty per cent of the specimens were sterile. more than 20 per cent of the bacterial species isolated from bronchial secretion were pathogenic. relatively frequent was the isolation of e. coli and of pathogenic sta ... | 1975 | 5823 |
| study of the penicillin amidase from e. coli. an ultrasonic method of studying the ph- and temperature-conformational transitions in the active center of the enzyme. | ph and temperature conformation transitions in the active center of penicillin amidase i.e. penicillinamidohydrolase e.c. 3.5.i.ii were investigated by means of the kinetic method and a new ultrasonic method. it was shown that the catalytic activity of the enzyme was controlled by 2 ionogenic groups with pk 6.1 and 10.2. the study of penicillinamidase by means of the ultrasonic method showed that the ionogenic group with pk 10 was responsible for maintaining the catalytically active conformation ... | 1976 | 5943 |
| proton translocation and the respiratory nitrate reductase of escherichia coli. | stoicheometries and rates of proton translocation associated with respiratory reduction of no3- have been measured for spheroplasts of escherichia coli grown anaerobically in the presence of no3-. observed stoicheiometries leads to h+/no3- ratio; p. mitchell (1966) chemiosmotic coupling in oxidative and photosynthetic phosphorylation, glynn research, bodmin were approx. 4 for l-malate oxidation and approx. 2 for succinate, d-lactate and glycerol oxidation. measurements of the leads to h+/2e- rat ... | 1975 | 5996 |
| succinate uptake and related proton movements in escherichia coli k12. | 1. the apparent km values for succinate uptake by whole cells of escherichia coli k12 depend on ph in the range 6.5-7.4.2. uptake of succinate in lightly buffered medium is accompanied by proton uptake. 3. the apparent km values for succinate uptake and for succinate-induced proton uptake are similar. 4. approximately two protons enter the cell with each succinate molecule. 5. the pattern of inhibition of succinate uptake is similar to that of succinate-induced proton uptake. 6. uptake of fumara ... | 1975 | 5999 |
| transport and utilization of the biosynthetic intermediate shikimic acid in escherichia coli. | auxotrophic mutants of escherichia coli w or k12 blocked before shikimic acid in the aromatic biosynthetic pathway grew poorly on shikimic acid as sole aromatic supplement. this poor growth response was correlated with a relatively poor ability to transport shikimic acid. if citrate was present in the growth medium (as it is in some commonly used basal media) the growth of some of the e. coli k12 mutants on shikimate was further reduced. mutants were derived from pre-shikimate auxotrophs which g ... | 1976 | 6050 |
| relationship between the magnitude of km and ph for l-asparaginase. | the dependency of l-asparagine hydrolysis rate on l-asparagine concentration in the presence of l-asparaginases from e. coli and erw. carotovora is studied in a broad ph range. km values are calculated from the data obtained. it is found that km insignificantly depends on ph value with the ph range of 5-9 for both asparaginases. sharp km maximum is observed at ph greater than 9 in both cases. the maximum position does not coinside with enzyme isoelectric points and with the region of the substra ... | 1976 | 6070 |
| modified 5'-nucleotides resistant to 5'-nucleotidase: isolation of 3-(3-amino-3-carboxypropyl) uridine 5'-phosphate and n2, n2-dimethylguanosine 5'-phosphate from snake venom hydrolysates of transfer rna. | a procedure for the quantitative measurement of the o2'-methylnucleoside constitutents of rna has recently been developed in this laboratory (gray, m.w. can. j. biochem. 53, 735-746 (1975)). this assay method is based on the resistance of o2'-methylnucleoside 5'-phosphates (pnm) (generated by phosphodiesterase hydrolysis of rna) to subsequent dephosphorylation by venom 5'-nucleotidase (ec 3.1.3.5). in the present investigation, two base-modified 5'-nucleotides, each displaying an unusual resista ... | 1976 | 6133 |