| selective enrichment of shigella in the presence of escherichia coli by use of 4-chloro-2-cyclopentylphenyl beta-d-galactopyranoside. | a procedure involving the use of citrate-buffered lactose broth (ph 6.5) containing an analogue of a beta-galactoside (4-chloro-2-cyclopentylphenyl beta-d-galactopyranoside) has been developed for the enrichment of shigella in competition with a 100-fold higher population of escherichia coli. the system makes use of the beta-galactosidase activity of e. coli which hydrolyzes the phenolic derivative of beta-galactoside to galactose and an aglycone moiety (4-chloro-2-cyclopentylphenol) which is to ... | 1976 | 6138 |
| antibacterial activity and pharmacokinetics of bacampicillin and ampicillin. | single equimolar oral doses of bacampicillin and ampicillin were given to 9 healthy subjects on a crossover randomized basis. data were interpreted in terms of a 3-compartment pharmacokinetic open model. intestinal absorption of bacampicillin was found to be faster and more complete than that of ampicillin, yielding an increase in bioavailability of 30% to 40% as measured by the area under serum levels curve, the urinary excretion and absorption rate constants. after the administration of bacamp ... | 1976 | 6181 |
| conformation of escherichia coli glutamic acid trna ii as studied by hydrogen-tritium exchange catalyzed by cysteine methyl ester. | incubation of cmp in 2h2o with 0.5m cysteine methyl ester at p2h 5 and 37 degrees c for 24 h resulted in 43% exchange of 5-h to 5-2h. no deamination of the cytosine nucleus was noted during this treatment. native and denatured dna samples from calf thymus were treated in 3h2o with cysteine methyl ester at ph 5 and 37 degrees c for 24 h and incorporation of tritium into each dna base was determined by enzymic digestion of the treated dna. the order of the specific radioactivity found was cytosine ... | 1976 | 6269 |
| chemical modification of streptovaricin c i. 19-o-substituted damavaricin c. | damavaricin c, a degradative derivative of streptovaricin c, has reduced antibiotic activity relative to streptovaricin c. it has, however, a new phenolic hydroxyl group at the c-19 position of the naphthoquinone ring on which various groups can be substituted through an ether linkage. a series of 19-o-substituted derivatives of damavaricin c has been synthesized. the preparation of these derivatives, their in vitro antibacterial activities, in vitro inhibition of e. coli rna polymerase, and let ... | 1976 | 6410 |
| comparative in vitro activity of cephalosporins. | the in vitro activity of cephalexin, cephaloridine, cephalothin, cephapirin, cefoxitin, cephamycin c, cepharadine and cefazolin was determined against 443 isolates of bacteria. at a concentration of 12.5 mug/ml, all of the cephalosporins inhibited more than 60% of the isolates of klebsiella pneumoniae. at the same concentration, cephalexin, cephaloridine, cephalothin, cephapirin, cephamycin c and cefazolin inhibited more than 90% of isolates of proteus mirabilis. all of the cephalosporins except ... | 1976 | 6411 |
| differentiation of mechanisms responsible for inoculum effects in the response of escherichia coli to a variety of antibiotics. | | 1976 | 6416 |
| regulation of histidase synthesis in intergeneric hybrids of enteric bacteria. | regulation of the expression of the histidase coded by hutk of klebsiella aerogenes in salmonella typhimurium and in escherichia coli and of the expression of the histidase coded by huts of s. typhimurium in e. coli was investigated. the hutk histidase was found to be sensitive to catabolite repression in k. aerogenes and in e. coli, but insensitive to catabolite repression in s. typhimurium; huts histidase has previously been shown to be catabolite sensitive in all three organisms. the expressi ... | 1976 | 6426 |
| glutamate dehydrogenase: genetic mapping and isolation of regulatory mutants of klebsiella aerogenes. | the gene for glutamate dehydrogenase (gdhd) has been mapped in klebsiella aerogenes by p1 transduction. it is linked to pyrf and trp with the order pyrf-trp-gdh. complementation analysis using f' episomes from escherichia coli suggests an analogous location in e. coli. two mutants able to produce glutamate dehydrogenase in the presence of high levels of glutamine synthetase have been isolated. one, tightly linked to gdhd, shows normal repression control by glutamine synthetase but produces four ... | 1976 | 6429 |
| adenosine 5'-triphosphate synthesis energized by an artificially imposed membrane potential in membrane vesicles of escherichia coli. | adenosine 5'-triphosphate (atp) synthesis driven by an artificially imposed membrane potential in right-side-out membrane vesicles of escherichia coli was investigated. membrane vesicles prepared in the presence of adenosine diphosphate were loaded with k+ by incubation with 0.5 m potassium phosphate. addition of valinomycin resulted in the synthesis of 0.2 to 0.3 nmol of atp/mg of membrane protein, whereas no synthesis was observed after addition of nigericin. addition of k+, dicyclohexylcarbod ... | 1976 | 6430 |
| regulation of enzyme formation in klebsiella aerogenes by episomal glutamine synthetase of escherichia coli. | we studied the physiology of cells of klebsiella aerogenes containing the structural gene for glutamine synthetase (glna) of escherichia coli on an episome. the e. coli glutamine synthetase functioned in cells of k. aerogenes in a manner similar to that of the k. aerogenes enzyme: it allowed the level of histidase to increase and that of glutamate dehydrogenase to decrease during nitrogen-limited growth. the phenotype of mutations in the glna site was restored to normal by the introduction of th ... | 1976 | 6431 |
| kinetic properties of serratia marcescens adenosine 5'-diphosphate glucose pyrophosphorylase. | the regulatory properties of partially purified adenosine 5'-diphosphate-(adp) glucose pyrophosphorylase from two serratia marcescens strains (atcc 274 and atcc 15365) have been studied. slight or negligible activation by fructose-p2, pyridoxal-phosphate, or reduced nicotinamide adenine dinucleotide phosphate (nadph) was observed. these compounds were previously shown to be potent activators of the adpglucose pyrophosphorylases from the enterics, salmonella typhimurium, enterobacter aerogenes, e ... | 1976 | 6432 |
| characterization of group b colicin-resistant mutants of escherichia coli k-12: colicin resistance and the role of enterochelin. | nine classes of group b colicin-resistant mutants were examined to study the role of enterochelin in colicin resistance. four of the mutants studied (cbt, exbc, exbb, and tonb) hypersecreted enterochelin. enterochelin hypersecretion was apparently responsible for resistance of the exbc mutant to colicins g and h and for resistance of the exbb mutant to colicins g, h, ia, ib, s1, and v. all four mutants scored as colicin b tolerant, even in the absence of enterochelin synthesis. the mutants produ ... | 1976 | 6433 |
| glutamate synthase. properties of the glutamine-dependent activity. | properties of glutamine-dependent glutamate synthase have been investigated using homogeneous enzyme from escherichia coli k-12. in contrast to results with enzyme from e. coli strain b (miller, r. e., and stadtman, e. r. (1972) j. biol. chem. 247, 7407-7419), this enzyme catalyzes nh3-dependent glutamate synthase activity. selective inactivation of glutamine-dependent activity was obtained by treatment with the glutamine analog. l-2-amino-4-oxo-5-chloropentanoic acid (chloroketone). inactivatio ... | 1976 | 6449 |
| properties of apoglutamate synthase and comparison with glutamate dehydrogenase. | glutamate synthase from escherichia coli k-12 exhibits nh3-dependent activity. nh3-dependent activity is increased approximately 5-fold in apoglutamate synthase lacking flavin and non-heme iron. whereas glutamine plus 2-oxoglutarate have the capacity to reoxidize the chemically reduced flavoenzyme, no such reoxidation is obtained with 2-oxoglutarate plus nh3. these results establish that the glutamine- and nh3-dependent syntheses of glutamate occur by different pathways of electron transfer from ... | 1976 | 6450 |
| regulation of glutaminase b in escherichia coli. i. purification, properties, and cold lability. | escherichia coli contains two glutaminases, a and b, with ph optima below ph 5 and above ph 7, respectively. neither glutaminase a nor b is released from e. coli by osmotic shock. glutaminase b has been purified 6,000-fold and the purified preparation is estimated to contain about 40% glutaminase b. the enzyme has a molecular weight of 90,000 and an isoelectric point of 5.4. glutaminase b exhibits a broad ph optimum between 7.1 and 9.0. only l-glutamine is deamidated by glutaminase b, l-asparagi ... | 1976 | 6454 |
| ketopantoate hydroxymethyltransferase. ii. physical, catalytic, and regulatory properties. | some physical, catalytic, and regulatory properties of ketopantoate hydroxymethyltransferase (5,10-methylenetetrahydrofolate: alpha-ketoisovalerate hydroxymethyltranferase) from escherichia coli are described. this enzyme catalyzes the reversible synthesis of ketopantoate (reaction 1), an essential precursor of pantothenic acid. (1) hc(ch3)2cocoo- + 5,10-methylene tetrahydrofolate f in equilibrium r hoch2c(ch3)2cocoo- + tetrahydrofolate it has a molecular weight by sedimentation equilibrium of ... | 1976 | 6463 |
| sea urchin sperm guanylate cyclase. purification and loss of cooperativity. | the lubrol-dispersed guanylate cyclase from sea urchin sperm was purified and isolated essentially free of detergent by gtp affinity chromatography, deae-sephadex chromatography, and gel filtration. after removal of the detergent, the enzyme remained in solution in the presence of 20% glycerol. the specific activity of the purified enzyme was about 12 mumol of guanosine 3':5'-monophosphate (cyclic gmp) formed - min-1 - mg of protein-1 at 30 degrees, an activity about 4600 times that of a soluble ... | 1976 | 6469 |
| biochemical characterization of mutant forms of dna polymerase i from escherichia coli. i. the pola12 mutation. | dna polymerase i has been purified to greater than 90% homogeneity from a strain of escherichia coli k12 that bears the temperature-sensitive dna polymerase i mutatation, pola12. the mutant enzyme has a reduced electrophoretic mobility and sedimentation rate. it is abnormally thermolabile and is rapidly inactivated at low salt concentrations. its polymerase and 5' leads to 3' exonuclease activities are not grossly defective at 30 degrees, yet its capacity to promote the concerted 5' leads to 3' ... | 1976 | 6470 |
| induced turbidity changes in non-growing cultures of escherichia coli. | | 1976 | 6711 |
| quantitative and qualitative determinations of the combined effect of tetracycline and oleandomycin. i. in vitro effect. | growth inhibitory effect of combined treatment of tetracycline (tc) and oleandomycin (om), at a ratio of 2:1, on certain species of pathogenic bacteria including drug-resistant ones was examined. by the crossed paper strip method, synergistic effects were demonstrated against 9 of the 16 strains of staphylococcus aureus, and all of the 5 strains of escherichia coli studied. antagonism was observed with none of the strains and with 2 strains of streptococcus pyogenes and 2 strains of streptococcu ... | 1976 | 6805 |
| the electrochemical gradient of protons and its relationship to active transport in escherichia coli membrane vesicles. | membrane vesicles isolated from e. coli generate a trans-membrane proton gradient of 2 ph units under appropriate conditions when assayed by flow dialysis. using the distribution of weak acids to measure the proton gradient (deltaph) and the distribution of the lipophilic cation triphenyl-methylphosphonium to measure the electrical potential across the membrane (delta psi), the vesicles are shown to generate an electrochemical proton gradient (deltamuh+) of approximately-180 mv at ph 5.5 in the ... | 1976 | 6961 |
| order of genes adjacent to ptsx on the e. coli genome. | | 1976 | 6969 |
| n-nitrosamine formation by cultures of several microorganisms. | of 38 pure cultures of microorganisms tested, only one, pseudomonas stutzeri, was capable of forming dimethylnitrosamine from dimethylamine and nitrite during growth. resting cells of p. stutzeri, cryptococcus terreus, escherichia coli, and xanthomonas campestris formed dimethylnitrosamine, although no nitrosamine was found in growing cultures of the latter three organisms. no nitrosamine was produced by either growing cultures or resting-cell suspensions of pseudomonas fragi or proteus mirabili ... | 1976 | 7197 |
| increased production of the outer membrane receptors for colicins b, d and m by escherichia coli under iron starvation. | | 1976 | 7254 |
| an investigation of an unusual histidyl residue in escherichia coli b l-asparaginase through fluorescence quenching. | the tryptophanyl fluorescence of escherichia coli b l-asparaginase is partially quenched by the protonated form of a base with pka 6.0 at 25 degrees c, mu = 0.1. this base has been identified as a histidyl residue through the effect of ionic strength and solvent polarity on the pka. in addition diethylpyrocarbonate which modifies two histidyl residues in the enzyme abolishes the fluorescenc titration and reduces enzymic activity by 90%. the temperature dependence of the histidine pka is unusual, ... | 1976 | 7304 |
| differential reaction of cell membrane phospholipids and proteins with chemical probes. | the major aims of this study were to determine the degree of phospholipid asymmetry and the neighbor analysis of phospholipids in different types of cell membranes. for this study a penetrating probe (fdnb), a non-penetrating probe (tnbs) and a cross-linking probe (dfdnb) were used. the reaction of hemoglobin, membrane protein and membrane pe and ps of erythrocytes with dfnb and tnbs was studied over a concentration range of 0.5 to 10 mm probe. tnbs reacts to an extremely small extend with hemog ... | 1976 | 7364 |
| influence of dna acidification on dna premelting and template properties. | acidification of a t7 dna sample was found to be partly irreversible as ultraviolet difference spectra measured at various sub-melting temperatures were different from those observed for a 'normal' dna sample. this implies some subtle conformational change which is not reversed by return to neutral ph. in the same conditions, only poly(purine)-poly(pyrimidine) polymers behaved in a different manner, during premelting, according to whether they were previously acidified or not. the properties of ... | 1976 | 7456 |
| iron uptake in colicin b-resistant mutants of escherichia coli k-12. | four classes of colicin b-resistant mutants of escherichia coli k-12 were examined for defects in iron uptake. all four mutant classes (cbt, exbc, exbb, and tonb) were defective in the uptake of ferri-ennterochelin. the tonb mutant was also defective in citrate-, ferrichrome-, and rhodoturulic acid-mediated iron uptake. the defects in iron transport were reflected in increased sensitivity to iron chelators and to chromium and aluminium salts, and in hypersecretion of enterochelin. one of the mut ... | 1976 | 7543 |
| magnitude of the protonmotive force in respiring staphylococcus aureus and escherichia coli. | the membrane potential and ph gradient developed across the plasma membranes of whole cells of staphylococcus aureus and spheroplasts of escherichia coli were estimated. the distributions of potassium ions in the presence of valinomycin and the ph gradient across the membrane were determined from the changes in pk and ph observed in the external medium during transition from the energized respiring state to the de-engerized resting condition. the protonmotive force in respiring cells was estimat ... | 1976 | 7546 |
| proton movements coupled to lactate and alanine transport in escherichia coli: isolation of mutants with altered stoichiometry in alanine transport. | the addition of lactate to lightly buffered suspensions of resting cells of escherichia coli caused an increase in the ph of the extracellular phase as lactate and protons entered the cell together. from the magnitude of the ph change and the non-electrogenic character of lactate uptake, we concluded that the stoichiometry of the process was 1 proton/lactate anion. the addition of alanine caused a slow increase in ph, also apparently due to the transport of the amino acid by a symport mechanism ... | 1976 | 7547 |
| role of l-threonine dehydrogenase in the catabolism of threonine and synthesis of glycine by escherichia coli. | the enzyme l-threonine dehydrogenase was demonstrated in extracts of escherichia coli k-12, and was shown to be the first enzyme of the pathway converting threonine to glycine. the enzyme was induced by l-leucine, but not by its substrate, l-threonine. the metabolic significance of leucine as a catabolic signal for amino acid degradation is considered. | 1976 | 7548 |
| partial characterization of a temperature-sensitive mutation affecting acetyl coenzyme a carboxylase in escherichia coli k-12. | a temperature-sensitive mutation in escherichia coli k-12 was shown to affect acetyl coenzyme a carboxylase and to map at min 63. this site is designated fabe. | 1976 | 7549 |
| determinants of lung bacterial clearance in normal mice. | the determinants of the lung clearance of streptococcus pneumoniae, klebsiella pneumoniae, escherichia coli, and staphylococcus aureus were studied in normal mice after exposure to an aerosol of viable bacteria and 99mtc-labeled dead bacteria. the fraction of bacteria in lungs that remained viable 4 h after exposure were: s. pneumoniae, 7.3%; k. pneumoniae, 121%; e. coli, 88.5%; s. aureus, 27.6%. the rate of physical removal of bacterial particles (kmc) was determined from the change in lung 99m ... | 1976 | 7575 |
| hydrogen donor system for escherichia coli ribonucleoside-diphosphate reductase dependent upon glutathione. | e. coli b tsnc 7004, an e. coli b/1 mutant with normal phenotype unable to replicate phage t7 dna chamberlin, m. (1974)j. virol. 14,509-516, contained no detectable level of thioredoxin when assayed with ribonucleotide reductase (2'-deoxyribonucleoside-diphosphate:oxidized-thioredoxin 2'-oxidoreductase, ec 1.17.4.1). gently lysed e. coli tsnc 7004 cell extracts reduced cdp when supplemented with nadph as efficiently as the parent strain e. coli b/1 despite the lack of thioredoxin, indicating the ... | 1976 | 7783 |
| alpha-hemolysin of e. coli. | the activity of alpha-hemolysin increased at the log growth phase in the culture of e. coli p678 hly+ hemolytic strain; this activity diminished with the change into the stationary phase, and then fell sharply. replacement of the culture medium in the stationary growth phase by fresh one led to restoration of the hemolytic activity of the culture. the culture fluid separated from the cells at the stationary growth phase produced an inhibitory action on the alpha-hemolysin ca ions activated and s ... | 1976 | 7907 |
| quantitation of local acidosis and hypoxia produced by infection. | increased strength of healing incisions infected with e coli was demonstrated in this experiment. efforts to measure respiratory gas tensions and ph in these incisions were unsuccessful. therefore, these moieties were measured in normal and infected wound fluid contained in implanted wire cylinders. the wound fluid from infected cylinders was consistently more acidotic and had a lower po2 and a higher pco2 than fluid from unifected wound cylinders. | 1976 | 7960 |
| study of e. coli penicillin amidase. the ph dependence of the equilibrium constant of the enzymatic hydrolysis of benzylpenicillin. | the equilibrium constant for penicillin amidase-catalyzed hydrolysis of benzylpenicillin(keg =3.00 +/- 0.24 x 10(-3) m at ph 5.0) and the ionization constants for phenylacetic acid (paa) and the amino groups of 6-aminopenicillanic acid (6-apa) were determined (4.20 and 4.60 under conditions of the kinetic experiments respectively). the experimental data at ph 6.0 satisfactorily correlated with the theoretical ph-dependence for keg constructed according to the hypothesis that benzylpenicillin syn ... | 1976 | 7996 |
| purification and properties of a new aminopeptidase from escherichia coli k12. | an aminopeptidase (ec 3.4.11.-) capmable of hydrolyzing l-alanyl-beta-naphthyl-amide and certain other aminoacyl beta-naphthylamides was purified to homogeneity from extracts of exherichia coli k-12. the enzyme, designated aminopeptidase ii, is a monomeric protein of mol. wt. 100 000. it exhibits a broad ph optimum in the range ph 7.0--9.0. although zn2+, fe3+ and cr3+ are strong inhibitors of enzyme activity, a metal requirement for catalysis could not be firmly established. neither sulfhydryl ... | 1976 | 8147 |
| role of lysyl-trna in the regulation of lysine biosynthesis in escherichia coli k12. | a mutant of lysyl-trna synthetase has been isolated in escherichia coli k12. with this strain the kmapp for lysine is 25 fold higher than with the parental strain. the percentage of charged trnalys in vivo is only 7 per cent (as against 65 per cent with hfr h). under these conditions no derepression of synthesis is observed for three lysine biosynthetic enzymes (ak iii, asa-dehydrogenase, dap-decarboxylase) ; a partial derepression is obtained in the case of the dhdp-reductase. thus lysyl-trna d ... | 1976 | 8152 |
| mechanistic studies of glutamine synthetase from escherichia coli. an integrated mechanism for biosynthesis, transferase, atpase reaction. | the mechanism of biosynthetic, transferase, atpase, and transphosphorylation reactions catalyzed by unadenylylated glutamine synthetase from e. coli was studied. activation complex(es) involved in the biosynthetic reaction are produced in the presence of either mg2+ or mn2+ ; however, with the mn2+-enzyme inhibition by the product, adp, is so great that the overall forward biosynthetic reaction cannot be detected with the known assay methods. binding studies show that substrates (except for nh3 ... | 1976 | 8153 |
| the mechanism of action of ppgpp on rrna synthesis in vitro. | we have studied the mechanism of the specific inhibition of ribosomal rna synthesis by ppgpp in a purified system using as templates e. coli dna and dna from lambdad5ilv, which carries a rrna cistron from e. coli. ribosomal rna synthesis, as well as its inhibition by ppgpp, are critically salt-dependent. of a number of guanosine phosphates tested, only pppgpp (ms ii) mimicked the action of ppgpp, establishing the specificity of ppgpp. the two templates gave similar results for rrna synthesis in ... | 1976 | 8211 |
| naturally occurring cross-links in yeast chromosomal dna. | chromosome-size yeast dna molecules with a number average molecular weight (mn) of 3-4 x 10(8) were isolated from sucrose gradients after sedimentation of lysed yeast spheroplasts. resedimentation showed that the molecules were isolated without introducing appreciable single-strand or double-strand breaks. the presence of cross-links in these molecules was suggested by the observation that the apparent mn in alkali was greater than expected for separated single strands. since cross-linked molecu ... | 1976 | 8214 |
| on the transport of tripeptide antibiotics in bacteria. | the two tripeptide antibiotics l-2-amino-4-methylphosphinobutyryl-alanyl-alanyl-alanine (l-phosphinothricyl-alanyl-alanine) and l-(n5-phosphono)methionine-s-sulfoximinyl-alanyl-alanine, both inhibitors of the glutamine synthetase, are transported into the cell of escherichia coli k 12 via the oligopeptide transport system. the uptake by this system is proved first of all by cross-resistance with tri-l-ornithine using oligopeptide-transport-deficient mutants, and secondly by antagonism tests demo ... | 1976 | 8311 |
| recombinant clone heterogeneity in escherichia coli conjunction: effect of ph and partially replicated recipient deoxyribonucleic acid. | at ph 6.8, a substantial fraction of recombinant colonies obtained from conjugation with an hfrh donor contained multiple recombinant classes in a single colony (polygenotype colony). in contrast, when the conjugation was performed at ph 7.6, the number of polygenotypic colonies was drastically reduced, and the recombinant colonies were predominantly monogenotypic or digenotypic. genetic analysis revealed that the digenotypic recombinants differ in those donor markers near the origin of dna repl ... | 1975 | 8360 |
| biological effects of escherichia coli lipopolysaccharide (lps) in vivo. i. selection in the mouse thymus of killer and helper cells. | in the present study we have investigated the biological effects on thymus lymphocytes resulting from escherichia coli lipopolysaccharide (lps) treatment in young adult mice. it has been established that lps induces the following effects: (a) a dose-dependent reduction of thymus weight contemporaneous with a rise in the anti-lps antibody response; (b) an increase of killer activity of thymus cells; (c) an enhancement of thymocytes helper activity; (d) a reduction of theta-positive cells in the t ... | 1976 | 8378 |
| constitutive and repressivle enzymes of the common pathway of aromatic biosynthesis in escherichia coli k-12: regulation of enzyme synthesis at different growth rates. | synthesis of five of the enzymes of the common pathway of aromatic biosynthesis has been shown to be unaffected by either the aromatic amino acids--the product of the first reaction (3-deoxy-d-arabinoheptulosonic acid-7-phosphate) or the product of the last reaction (chorismate)--or by the state of regulator gene loci tyrr. on the other hand, the rate of synthesis of these enzymes, and of several other enzymes for which repression control was inactive because of mutations in relevant regulator g ... | 1976 | 8426 |
| ornithine delta-transaminase activity in escherichia coli: its identity with acetylornithine delta-transaminase. | procedures that have been developed for the purification of acetylornithine delta-transaminase from escherichia coli w also lead to the simultaneous purification of ornithine delta-transaminase. these two enzymatic activities have the same electrophoretic mobility and are identical immunochemically. studies of inhibition kinetics demonstrate that the two substrates, acetylornithine and ornithine, compete for the same active site of acetylornithine delta-transaminase; thus, the ornithine delta-tr ... | 1976 | 8431 |
| deoxyribonucleic acid polymerase from the extreme thermophile thermus aquaticus. | a stable deoxyribonucleic acid (dna) polymerase (ec 2.7.7.7) with a temperature optimum of 80 degrees c has been purified from the extreme thermophile thermus aquaticus. the enzyme is free from phosphomonoesterase, phosphodiesterase and single-stranded exonuclease activities. maximal activity of the enzyme requires all four deoxyribonucleotides and activated calf thymus dna. an absolute requirement for divalent cation cofactor was satisfied by mg2+ or to a lesser extent by mn2+. monovalent catio ... | 1976 | 8432 |
| 5-iodo-5'-amino-2',5'-dideoxyuridine-5'-n'-triphosphate. synthesis, chemical properties, and effect on escherichia coli thymidine kinase activity. | 5-iodo-5'-amino-2',5'-dideoxyuridine-5'-n'-triphosphate (aidutp), a phosphoramidate analog of 5-iodo-2',5'-dideoxyuridine 5'-triphosphate (idutp), was synthesized and some of its chemical and biological properties were investigated. although aidutp is stable in alkaline solutions, below ph 8 it undergoes degradation by a novel phosphorylysis reaction which exhibits first order kinetics. inclusion of magnesium ion in the reaction mixture decreased the rate of degradation. protonation of a group o ... | 1976 | 8448 |
| oxidative phosphorylation in right-side-out membrane vesicles from escherichia coli. | oxidative phosphorylation in escherichia coli membrane vesicles with a right-side-out orientation and loaded with adp was investigated. substrates of the electron transport chain could energize the phosphorylation of adp, with the order of effectiveness being d-lactate greater than reduced phenazinemethosulfate greater than succinate greater than reduced nicotinamide adenine dinucleotide. inhibitors of d-lactate oxidation, proton conductors, and inhibitor of the mg2+atpase (ec 3.6.1.3) all inhib ... | 1976 | 8460 |
| formation of ethylene by escherichia coli. | escherichia coli strain spa o converts methionine to ethylene by an inducible enzyme system. l-cysteine, l-homocysteine, methionine derivatives and the sulphur-containing analogues of l-methionine also act as precursors of ethylene. ethylene is produced by cell suspensions only in the presence of air; cell-free preparations can produce ethylene aerobically and anaerobically, but the extent to which they do so depends on the mode of culture growth. light stimulates ethylene production by cell sus ... | 1976 | 8586 |
| bifidobacteria in the intestinal tract of infants: an in-vivo study. | weekly faecal specimens from 18 babies were examined during the first 8 weeks of life. eight infants were breast fed, ten were bottle-fed. all suckling infants received supplementary feeds for the first 8 days. a buffer consisting of acetic acid and acetate was demonstrated in the faeces of all the breast-fed infants at some time during the period of examination. this buffer was rarely detected during the 1st week of life when supplementary feeds were given, and buffer already present gradually ... | 1976 | 8646 |
| affinity labelling of phenylalanyl-trna synthetase from e. coli mre-600 by e. coli trnaphe containing photoreactive group. | the photoinduced reaction of phenylalanyl-trna synthetase (e.c.6.1.1.20) from e.coli mre-600 with trnaphe containing photoreative p-n3-c6h4-nhcoch2-group attached to 4-thiouridine su8 (azido-trnaphe) was investigated. the attachment of this group does not influence the dissociation constant of the complex of phe-trnaphe with the enzyme, however it results in sevenfold increase of km in the enzymatic aminoacylation of trnaphe. under irradiation at 300 nm at ph 5.8 the covalent binding of 14c-phe- ... | 1976 | 8772 |
| effect of escherichia coli endotoxin on liver macrophages during the graft versus recipient response. | | 1976 | 8939 |
| resistance to levomycetin and activity of several enzymes in escherichia coli and the agent of plague. | the authors compared the activity of acetyl-coa-synthetase and of the enzymes belonging to the group of asparaginic acid in levomycetin sensitive and resistant strains of y. pestis and e. coli. there were revealed marked differences in the activity of aspartase, fumarase, synthetase and desamidase of l-asparagin, and also of the enzyme activated by acetate in the e. coli strains with plasmide resistance. transmission of r-factor to the pestis was accompanied by decomposition of l-asparadein, for ... | 1976 | 8940 |
| ulcerative rectocolitis. somatic aspects (author's transl). | regional enteritis (crohn's disease) and ulcerative rectocolitis, both "non specific inflammatory diseases of the bowel", might be diseases with a common etiology but with clinical features corresponding to a different tissular response to a noxious factor. both diseases are however characterized by distinct clinical, radiological, histological peculiarities; evolution also is different, as appears from the rarity of malignant degeneration in crohn's disease and its frequence in ulcerative colit ... | 1975 | 8957 |
| antibacterial activity of sisomicin in comparison with gentamicin. | the antibacterial activity of sisomicin -- a new aminoglycoside antibiotic -- as compared with gentamicin was tested on 521 bacterial strains of different species in a serial-dilution test. staphylococci, streptococci, e. coli, klebsialla-enterobacter, indole-psitive proteus strains, pseufomonads, salmonads, salmonellae, and serratia marcescens were inhibited to the extent of 100% at a maximun of 4.0 mug/ml. sisomicin showed a higher antibacterial activity against part of the bacterial species. ... | 1976 | 9099 |
| effect of inhibitors on the substrate-dependent quenching of 9-aminoacridine fluorescence in inside-out membrane vesicles of escherichia coli. | the effect of various inhibitors on the substrate-dependent quenching of the fluorescence of 9-aminoacridine was measured in inside-out membrane vesicles of escherichia coli. the rate of fluorescence quenching in the presence of inhibitors was dependent on the rate of electron transfer through the respiratory chain with nadh, succinate, d-lactate or dl-glycerol 3-phosphate as substrates. several patterns of response were given by the inhibitors. inhibitors competitive with substrate, or those ac ... | 1976 | 9275 |
| distinct steps in the specific binding of trna to aminoacyl-trna synthetase. temperature-jump studies on the serine-specific system from yeast and the tyrosine-specific system from escherichia coli. | the kinetics of the interaction of trnaser and seryl-trna synthetase from yeast as well as of trnatyr and tyrosyl-trna synthetase from escherichia coli have been investigated by temperature-jump experiments. it could be shown that complex formation proceeds in two distinct steps. this was demonstrated for both the first and the second binding site. the two-step mechanism was deduced from the characteristic concentration dependence of the relaxation times. seryl-trna synthetase recombines with th ... | 1976 | 9287 |
| mechanism of discrimination between cognate and non-cognate trnas by phenylalanyl-trna synthetase from yeast. | the interaction between phenylalanyl-trna synthetase from yeast and escherichia coli and trnaphe (yeast), trnaser (yeast), trna1val (e. coli) has been investigated by ultracentrifugation analysis, fluorescence titrations and fast kinetic techniques. the fluorescence of the y-base of trnaphe and the intrinsic fluorescence of the synthetases have been used as optical indicators. 1. specific complexes between phenylalanyl-trna synthetase and trnaphe from yeast are formed in a two-step mechanism: a ... | 1976 | 9288 |
| current resistence situation in a surgical and urological department. | spectrum and sensitivity of bacteria were studied at the surgical (534 positive wound smears) and the urological clinics (7879 urine specimens). krankenhaus nordwest, frankfurt/m., during the period of 1969-1971 and in 1973. the most common organisms identified in wound smears were e. coli, followed by staph. areus, aerobacter and proteus species. e. coli were also predominant in urine, but followed by enterococci, proteus and pseudomonas. e. coli, proteus species and especially pseudomonas incr ... | 1976 | 9344 |
| factors influencing heat-labile escherichia coli enterotoxin activity. | in this study, conditions for production, detection, and storage of heat-labile escherichia coli enterotoxin (lt) in culture filtrates from e. coli h-10407 were defined by using the adrenal tumor cell assay system. an enriched medium containing 0.6% yeast extract, 2% casamino acids, and 0.25% glucose buffered at ph 8.5 produced the highest lt activity of the various test media. in e. coli strain h-10407, lt activity was markedly decreased if the initial ph of the culture media was reduced to ph ... | 1976 | 9363 |
| purification and characterization of beta-n-acetylhexosaminidases and beta-galactosidase from streptococcus 6646 k. | three beta-n-acetylhexosaminidases ec 3.2.1.52 and one beta-galactosidase ec 3.2.1.23 were purified from the culture filtrate of streptococcus 6646 group k by a combination of column chromatographies on p-aminophenyl beta-d-thiogalactopyranoside-substituted sepharose and n-(paminophenyl)oxamic acid-substituted sepharose. these beta-n-acetylhexosaminidases showed optimal activities between ph 5.0 and 5.5 and could hydrolyze synthetic and glycopeptidic substrates. glycolipids such as gm2, asialo-g ... | 1976 | 9384 |
| 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase. purification, properties, and kinetics of the tyrosine-sensitive isoenzyme from escherichia coli. | the tyrosine-sensitive 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (7-phospho-2-keto-3-deoxy-d-arabino-heptonate d-erythrose-4-phosphate lyase (pyruvate-phosphorylating), ec 4.2.1.15) was purified to homogeneity from extracts of escherichia coli k12. a spectrophotometric assay of the enzyme activity, based on the absorption difference of substrates and products at 232 nm, was developed. the enzyme has a molecular weight of 66,000 as judged by gel filtration on sephadex g-200, and a subu ... | 1976 | 9387 |
| rapid transfer of oxygens from inorganic phosphate to glutamine catalyzed by escherichia coli glutamine synthetase. | measurements are reported on certain isotopic fluxes during the net conversion of glutamine, adp and pi to glutamate, nh3, and atp by escherichia coli glutamine synthetase (adenylylated form, mn2+ activated) in presence of a hexokinase/glucose trap to remove the atp formed during the reaction. the results show that the transfer of oxygens from pi to glutamine is the most rapid of the measured isotopic interchanges, over five oxygens from pi being transferred to glutamine for each glutamate forme ... | 1976 | 9391 |
| a stereochemical method for detection of atp terminal phosphate transfer in enzymatic reactions. glutamine synthetase. | an isotope scrambling method is described for the detection of transient enz:adp:p-x formation from 18oatp in atp-coupled enzyme reactions. the method makes use of torsional symmetry of the newly formed (see article) group in adp. 18 oatp labeled in the betagama bridge oxygen was incubated with enzyme and reversible cleavage of the pbetao -- pgamma bond was detected by the appearance of 18o in the beta nonbridge oxygens of the atp pool. experiments with sheep brain and escherichia coli glutamine ... | 1976 | 9406 |
| the nadh dehydrogenase of the respiratory chain of escherichia coli. ii. kinetics of the purified enzyme and the effects of antibodies elicited against it on membrane-bound and free enzyme. | the purified respiratory chain nadh dehydrogenase of escherichia coli oxidizes nadh with either dichlorophenolindophenol (dcip). ferricyanide, or menadione as electron acceptors, with values for nadh are similar with the three electron acceptors (approximately 50 mum). the purified enzyme contains no flavin and has an absolute requirement for fad, with km values around 4 mum. the ph optimum of the enzyme appears to be between 6.5 and 7; the optimum is difficult to establish because of nonenzymat ... | 1976 | 9408 |
| aspartate transcarbamylase of escherichia coli. heterogeneity of binding sites for carbamyl phosphate and fluorinated analogs of carbamyl phosphate. | some preparations of both native aspartate transcarbamylase from escherichia coli and catalytic subunit have fewer tight binding sites per oligomer for carbamyl-p than the number of catalytic peptide chains. in contrast, the number of sites for the tight-binding inhibitor n-(phosphonacetyl)-l-aspartate does equal the number of catalytic chains in each case. binding of the labile carbamyl-p was determined using rapid gel filtration, with conversion to stable carbamyl-l-aspartate during collection ... | 1976 | 9409 |
| evidence from 13c nmr for protonation of carbamyl-p and n-(phosphonacetyl)-l-aspartate in the active site of aspartate transcarbamylase. | nuclear magnetic resonance has been used to study the binding of 13ccarbamyl-p (90% enriched) to the catalytic subunit of escherichia coli aspartate transcarbamylase. upon forming a binary complex, there is a small change in the chemical shift of the carbonyl carbon resonance, 2 hz upfield at ph 7.0, indicating that the environments of the carbonyl group in the active site and in water are similar. when succinate, an analog of l-aspartate, is added to form a ternary complex, there is a large dow ... | 1976 | 9410 |
| enzymatic action of coliphage omega8 and its possible role in infection. | the receptor of coliphage omega8 is the o-specific mannan of escherichia coli o8 in which the trisaccharide alpha-mannosyl-1,2-alpha-mannosyl-1,2-mannose is joined through alpha-mannosyl-1,3-linkages. coliphage omega8 produces an endo-alpha-1,3-mannosidase which destroys the receptor, liberating a series of oligosaccharides (repeating trisaccharide and multiples). the enzyme is an integral part of the phage particles and also occurs in a free form in the lysates. phage particles hydrolyze alpha- ... | 1976 | 9521 |
| defective polymorphonuclear leukocyte chemotaxis and bactericidal capacity in a boy with recurrent pyogenic infections. | a 13-year-old boy with a history of recurrent pyogenic infections had abnormalities of polymorphonuclear leukocyte (pmn) function which probably accounted for his susceptibility to infection. pmn phagocytosis and nitroblue tetrazolium dye reduction were normal but glucose 14c oxidation was abnormally increased in resting cells. the patient's pmns possessed decreased bactericidal activity against staphylococcus aureus and escherichia coli. also documented were decreased pmn chemotactic activity a ... | 1976 | 9619 |
| suppression of lytic effect of beta lactams on escherichia coli and other bacteria. | growth of e. coli at ph 5 protected the bacteria against the lytic effect of beta lactam antibiotics typically observed when the cells are grown at ph 7 or 7.5, i.e., the ph values routinely used in laboratory experiments. in contrast, the typical effects of beta lactam antibiotics on cellular shape and elongation and cell division appeared to be similar in cultures grown under neutral and acid ph conditions. the ph-dependent antibiotic tolerance can also be demonstrated with pneumococci, staphy ... | 1976 | 9642 |
| in vitro studies on the antimicrobial effects of colostrum and milk from vaccinated and unvaccinated pigs on escherichia coli. | unsupplemented porcine colostrum and milk exhibited a powerful bactericidal effect for porcine strains of e coli incubated in vitro at 37 degrees c. this activity was independent of complement but was susceptible to acid ph, to the presence of soluble iron and to the selective immunoprecipitation of igg, iga and igm. manifestation of bactericidal activity required bacteria in an active state of metabolism and the length of incubation was an important factor in demonstrating the quality of the an ... | 1976 | 9677 |
| intracellular protein breakdown. vii. cathepsin l and h; two new proteinases from rat liver lysosomes. | some properties (molecular weight, pi, temperature stability, action of selected inhibitors, substrate specificity and ph-activity dependence) of two not yet known cathepsins from rat liver lysosomes are compared with the properties of the known cathepsin b1. cathepsin l is a thiolproteinase, has a molecular weight of 23--24000 and a pi of 5,8--6,1. by disc electrophoresis and isoelectric focusing there appear several protein bands which all have enzymatic activity. leupeptin behaves as a strong ... | 1976 | 9766 |
| regulation of lysine biosynthesis in escherichia coli k12. | a general survey of the regulation in lysine biosynthesis in escherichia coli k12 is presented. no polygenic operon exists for the genes that code for enzymes of the lysine biosynthetic pathway. lysyl-trna is not directly involved as a co-repressor in the pathway. different regulation mechanisms must exist for the different enzymes. in the case of the last enzyme, diaminopimelate decarboxylase, its synthesis is induced in vivo by the lysine-sensitive aspartokinase under its non-inhibited alloste ... | 1976 | 9781 |
| regulation of tyrosine and phenylalanine biosynthesis in salmonella. | several types of 4-fluorophenylalanine resistant mutants were isolated. in one type of mutant dahp synthetase (tyr) and prephenate dehydrogenase were coordinately derepressed. the mutation was linked to arof and tyra and was cis- dominant by merodiploid analysis, thus confirming that it is an operator constitutive mutation (tyroc). a second type of mutation showed highly elevated levels of tyrosine pathway enzymes which were not repressed by l-tyrosine. it was unlinked to tyra and arof, and was ... | 1976 | 9783 |
| molecular and catalytic properties of the acetoacetyl-coenzyme a thiolase of escherichia coli. | | 1976 | 9904 |
| steady state kinetic analysis of the mechanism of guanosine triphosphate hydrolysis catalyzed by escherichia coli elongation factor g and the ribosome. | the mechanism of guanosine triphosphate (gtp) hydrolysis catalyzed by elongation factor g and the ribosome in the absence of other participants in protein synthesis was examined by steady-state kinetic analysis. optimal hydrolytic conditions were determined to be approximately ph 8.0, 20 mm mg2+, and 80 mm nh4+. kinetic analyses were performed under these conditions at constant elongation factor g concentrations and variable ribosome and gtp concentrations. the resulting double-reciprocal plots ... | 1976 | 9976 |
| identification of a ribonuclease p-like activity from human kb cells. | an endoribonuclease which cleaves trna precursor molecules has been partially purified from human kb tissue culture cells. this activity is found in cytoplasmic fractions but is not detectable in the nucleoplasm. trna precursor molecules from both e. coli and kb cells are cleaved by this novel activity to produce 5' phosphate-terminated oligonucleotides. e coli rnaase p and the kb cell nuclease both make a single endonucleolytic scission in e. coli trnatyr precursor, thereby separating the 41 ex ... | 1976 | 10085 |
| photochemical studies and ultraviolet sensitization of escherichia coli thymidylate kinase by various halogenated substrate analogs. | the effect of 5-iodo-2'-deoxyuridine monophosphate (idump), various 5-halogenated-5'-azido-2', 5' -dideoxyuridine derivatives, 2'-deoxy-6-azauridine (azdurd), and its halogenated analogs on the ultraviolet sensitization of escherichia coli thymidylate kinase has been investigated. only those compounds iodinated in position 5 enhance the rate of ultraviolet inactivation of this enzyme. however, 5'-azido nucleosides with iodo, bromo, chloro, or fluoro substituents in position 5 neither protect nor ... | 1976 | 10301 |
| the occurrence of salmonellas, mycobacteria and pathogenic strains of escherichia coli in pig slurry. | ninety-eight samples of pig slurry from 54 farms were examined for the presence of salmonellas, porcine enteropathogenic strains of haemolytic escherichia coli and mycobacteria. salmonellas were isolated from 12 farms (22%) and enteropathogenic e. coli from 13 farms (24%). pathogenic mycobacteria were not isolated. salmonellas were isolated from 7 of 16 farms (44%) stocked with 'minimal disease' pigs compared with only 5 of 38 farms (13%) stocked with conventionally reared pigs. conversely enter ... | 1976 | 10332 |
| pneumococcal antigen in pneumonia. a post-mortem study with the histological and bacteriological findings. | pneumococcal capsular antigens can be detected in lung tissue by counter-current immunoelectrophoresis even when, following antibiotics, post-mortem bacterilogy suggests that escherichia coli has replaced pneumococci. the results suggest that antipneumococcal therapy would benefit at least 55% of patients critically ill with lung infection and that the potentially toxic drugs directed at coliform bacteria may be unnecessary. | 1976 | 10565 |
| in vitro study of netilmicin compared with other aminoglycosides. | netilmicin (sch 20569) is an ethyl derivative of gentamicin c(1a) that is active against most enterobacteriaceae, pseudomonas aeruginosa, and staphylococcus aureus isolates. among 342 clinical isolates tested, all staphylococci; 92% of escherichia coli, 93% of klebsiella pneumoniae, and 92% of enterobacter were inhibited by 0.8 mug or less of netilmicin per ml, but only 78% of p. aeruginosa were inhibited by 3.1 mug or less per ml. most clinical isolates of enterococci, serratia marcescens, and ... | 1976 | 10829 |
| growth of physarum gyrosum on agar plates and in liquid culture. | the physical and nutritional requirements of the antibiotic-producing slime mold physarum gyrosum were examined to develop a liquid medium for this myxomycete. liquid culture is desired to expedite a useful scale of production of antibiotic materials for ease of isolation and structure study. culture conditions were selected to favor antibiotic production rather than maximum growth. the medium devised consisted of 0.010 m potassium phosphate buffer (ph 6.0), 2% bakers' yeast, and 0.2% glucose an ... | 1976 | 10830 |
| studies on the noncooperative binding of the escherichia coli dna unwinding protein to single-stranded nucleic acids. | the noncooperative binding of the escherichia coli dna unwinding protein to single-stranded dna oligomers has been studied by means of equilibrium dialysis. dialyses were performed under a number of solution and temperature conditions using oligomers of varying length and base compositions. the results of these studies, which include a scatchard analysis of the binding, have allowed us to propose a model for the cooperative binding of the protein to single-stranded dna. the results of experiment ... | 1976 | 10965 |
| purification and positional specificity of sn-glycerol-3-phosphate acyltransferase from escherichia coli membranes. | sn-glycerol-3-phosphate acyltransferase was solubilized from membranes of escherichia coli b and k-12 and purified on an affinity column of sepharose 4b coupled with 6-phosphogluconic acid. phosphatidylglycerol was required for activation and stabilization of the purified enzyme. the acyl residues were exclusively transferred to the position 1 of sn-glycerol 3-phosphate by the enzyme, regardless of whether the acyl-coa was saturated or unsaturated. | 1976 | 10989 |
| studies on aspartase. iii. alteration of enzymatic properties upon trypsin-mediated activation. | highly purified aspartase (l-aspartate ammonia-lyase, ec 4.3.1.1) from escherichia coli, already of full activity, is further activated 3.3-fold by limited treatment with trypsin. the activation requires a few minutes to attain maximum level, and hereafter the activity gradually decreases to complete inactivation. prior or intermediate addition of soybean trypsin inhibitor results in an immediate cessation of any further change in the enzyme activity. upon trypsin-mediated activation no apprecia ... | 1976 | 10995 |
| approach to a practical method for screening and identifying microorganism genera from urine (author's transl). | in this study the author reported upon a practical new system for screening and identifying the microbial agents causing urinary tract infections. this system is composed of a combination of 3 screening procedures (ph-value + nitrite-test + catalase-test) and 8 selective culture media for the purpose of genus identification within 24 hours (uripret-g). a total of 130 cultures was investigated. the employed microorganisms were mainly recovered from urine samples. they included the following speci ... | 1976 | 11179 |
| thermal fragmentation of escherichia coli beta-galactosidase. isolation and characterization of an alpha-complementing and two non-complementing polypeptide fractions. | carboxymethylated escherichia coli beta-galactosidase ec 3.2.1.23 could be broken to polypeptides of fairly uniform size (average molecular weight about 22,000 daltons) by heating for less than or equal to 8 h at 100 degrees c and ph 7.5 in 8 m-urea. using phosphocellulose chromatography in nacl-urea gradients, the resulting polypeptide mixture could be resolved in three fractions essentially homogeneous by disc gel electrophoresis in urea at several ph values, and by isoelectric focusing. one o ... | 1976 | 11192 |
| unique aspects of the regulation of the aspartate transcarbamylase of serratia marcescens. | aspartate trancarbamylase (atc ase; ec 2.1.3.2) from serratia marcescens hy has been purified 134-fold. its properties are unique. unlike the atcase from escherichia coli and salmonella typhimurium, the s. marcescens hy enzyme activity is not feedback inhibited by any purine or pyrimidine nucleotide effectors; instead, the enzyme is activated by both cytidine 5'-triphosphate and adenosine 5'-triphosphate. like the atcase from e. coli and s. typhimurium, adenosine 5'-triphosphate alters the s0.5 ... | 1976 | 11207 |
| purification and characterization of l-asparaginase with anti-lymphoma activity from vibrio succinogenes. | homogeneols l-asparaginase with anti-lymphoma activity was prepared from vibrio succinogenes, an anaerobic bacterium from the bovine rumen. an overall yield of pure l-asparaginase of 40 to 45% and a specific activity of 200 +/- 2 iu per mg of protein was obtained. the pure enzyme can be stored at -20 degrees for at least 3 months with no loss of activity. the isoelectric point of the l-asparaginase is 8.74. no carbohydrate, phosphorus, tryptophan, disulfide, or sulfhydryl groups were detected. t ... | 1976 | 11211 |
| the effect of colicin e1 on proton extrusion and the h+/0 ration in escherichia coli. | | 1976 | 11793 |
| fluorine-containing analogues of intermediates in the shikimate pathway. | the phosphoenolpyruvate analogue (z)-phosphoenol-3-fluoropyruvate is a substrate for phenylalanine-inhibitable 3-deoxy-d-arabino-heptulosonic acid-7-phosphate synthase from escherichia coli. in the presence of excess erythrose 4-phosphate, apparent km values of 65 and 38 mum were observed for phosphoenol-3-fluoropyruvate and phosphoenolpyruvate, respectively. because the apparent vmax for phosphoenol-3-fluoropyruvate is only 1.17% of that for phosphoenolpyruvate, one can study the former as an i ... | 1976 | 11811 |
| the shikimate pathway. iii. 3-dehydroquinate synthetase of e. coli. mechanistic studies by kinetic isotope effect. | the conversion of 3-deoxy d-arabino heptulosonate 7-phosphate to 3-dehydroquinate by the 3-dehydroquinate synthetase from e. coli is characterized by a low but significant kinetic isotope effect for tritium carried in position-5 of dahp, while no isotope effect was detectable for tritium in position-4. this effect was observed at different ph nad is interpreted as a result of theintermediary of a 5-ketonic form of the substrate, formed in a preliminary non limiting step during the enzymic cycliz ... | 1976 | 11839 |
| nuclear magnetic resonance studies of redox-induced conformational changes in thioredoxin from escherichia coli. | | 1976 | 12009 |
| microbicidal mechanisms of human granulocytes: synergistic effects of granulocyte elastase and myeloperoxidase or chymotrypsin-like cationic protein. | the antibacterial activity of a myeloperoxidase (mpo)-glucose oxidase system was found to be greatly increased by granulocyte elastase, present in azurophil granules of human neutrophils. the mpo-h2o3-mediated killing of both escherichia coli and staphylococcus aureus was potentiated by granuocyte elastase at an acid ph, whereas at ph 7.4 only killing of e. coli was potentiated. the potentiating effect of elastase was not dependent on the enzymatic properties of the protein since it was not abol ... | 1976 | 12111 |
| partial purification and some properties of delta1-pyrroline-5-carboxylate reductase from escherichia coli. | delta1-pyrroline-5-carboxylate (pca) reductase l-proline:nad(p)+5-oxidoreductase, ec 1.5.1.2 has been purified over 200-fold from escherichia coli k-12. it has a molecular weight of approximately 320,000. pca reductase mediates the pyridine nucleotide-linked reduction of pca to proline but not the reverse reaction (even at high substrate concentrations). the partially purified preparation is free of competing pyridine nucleotide oxidase, pca dehydrogenase, and proline oxidase activities. the mic ... | 1977 | 12133 |
| catalytic mechanisms of glutamine synthetase enzymes. studies with analogs of possible intermediates and transition states. | glutamine synthetase enzymes isolated from pea seeds and from escherichia coli are observed to behave differently in experiments designed to probe reaction mechanism. although both enzymes were found to bind and release substrates in random order mechanisms (wedler, f.c. (1974) j. biol. chem, 247, 5080-5087), isotopic exchanges with partial reaction systems indicative of a gamma-glutamylphosphate intermediate are catalyzed only by the pea seed enzyme. the e. coli system fails to catalyze any exc ... | 1976 | 12170 |
| a new endoribonuclease from escherichia coli. ribonuclease n. | a new ribonuclease called rnase n was isolated from escherichia coli. it is a nonspecific endoribonuclease that can cleave rrna, poly(u), and poly(c) to small oligonucleotides and 5'-mononucleotides. it requires monovalent cations and is inhibited by divalent cations. it is suggested that this enzyme plays a role in the decay of rrna,under various starvation conditions and perhaps in the decay of mrna. | 1976 | 12174 |
| r factor elimination from escherichia coli by hydroxyurea and cytosine arabinoside proceedings. | | 1976 | 12327 |