Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q17RS7 (Gen)
 130,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pyruvate carboxylase of Pseudonomas fluorescens was purified 160-fold from cells grown on glucose at 20 degrees C. The activity of this purified enzyme was not affected by acetyl-coenzyme A or L-aspartate, but was strongly inhibited by ADP, which was competitive towards ATP. Pyruvate gave a broken double reciprocal plot, from which two apparent Km values could be determined, namely 0-08 and 0-21 mM, from the lower and the higher concentration ranges, respectively. The apparent Km for HCO3 at pH 6-9, in the presence of the manganese ATP ion (MnATP2-), was 3-1 mM. The enzyme reaction had an optimum pH value of 7-1 or 9-0 depending on the use of MnATP2- or MgATP2-, respectively, as substrate. Free Mg2+ was an activator at pH values below 9-0. The enzyme was strongly activated by monovalent cations; NH4+ and K+ were the better activators, with apparent Ka values of 0-7 and 1-6 mM, respectively. Partially purified enzymes from cells grown on glucose at 1 or 20 degrees C had the same properties, including the thermal stability. In both cases 50% of the enzyme activity was lost after pre-incubation for 10 min at 46 degrees C. The molecular weight was estimated to be about 300000 daltons by gel filtration on Sephadex G-200. The regulatory properties and molecular weight are thus similar to those determined for the pyruvate carboxylases from Pseudomonas citronellolis and Azotobacter vinelandii.
J Gen Microbiol 1976 Mar
PMID:Some properties of the pyruvate carboxylase from Pseudomonas fluorescens. 0 79

The value of the adenylate energy charge, i.e. ([ATP] + 1/2[ADP])/([ATP] + [ADP] + [AMP]), during batch culture of Beneckea natriegens remained relatively constant during the exponential and early stationary phases of the growth cycle. During exponential growth the intracellular ATP content remained constant, the amount of ATP in the culture increasing proportionally with growth; these conditions were unaltered during growth in the presence of added cyclic AMP. On cessation of growth, significant variation in bacterial ATP content was observed depending on whether growth of the cultures terminated due to exhaustion of carbon or nitrogen from the medium, and on the presence or absence of added cyclic AMP.
J Gen Microbiol 1977 Jan
PMID:Adenylate energy charge during batch culture of Beneckea natriegens. 1 48

Choline, a component of the wall teichoic acid of Streptococcus pneumoniae, was converted to cytidine diphosphocholine via choline phosphate by enzymes which were identified in cell-free extracts of the pneumococcus. The first enzyme, choline kinase, was investigated in some detail. It appeared to have a pH optimum of 7.3 to 7.4 and was stimulated by Mg2+. Kinetic studies gave an apparent Michaelis constant (Km) for ATP of I mM, and for choline of 0.19 mM, with Vmax values of 3 nmol min-1 (mg protein)-1 and 0.5 nmol min-1 (mg protein)-1 respectively. The second enzyme, CDPcholine pyrophosphorylase was specific for CTP and had a requirement for Mg2+ with an optimum at 7 mM.
J Gen Microbiol 1977 May
PMID:The biosynthesis of a choline nucleotide by a cell-free extract from Streptococcus pneumoniae. 1 50

Mutants of Escherichia coli K12 have been isolated that grow on media containing pyruvate of proline as sole carbon sources despite the presence of 10 or 50 mM-sodium fluoroacetate. Such mutants lack either acetate kinase [ATP: acetate phosphotransferase; EC 2.7.2.1] or phosphotransacetylase [acetyl-CoA: orthophosphate acetyltransferase; EC 2.3.1.8] activity. Unlike wild-type E. coli, phosphotransacetylase mutants do not excrete acetate when growing aerobically or anaerobically on glucose; their anaerobic growth on this sugar is slow. The genes that specify acetate kinase (ack) and phosphotransacetylase (pta) activities are cotransducible with each other and with purF and are thus located at about min 50 on the E. coli linkage map. Although Pta- and Ack- mutants are greatly impaired in their growth on acetate, they incorporate [2-14C]acetate added to cultures growing on glycerol, but not on glucose. An inducible acetyl-CoA synthetase [acetate: CoA ligase (AMP-forming); EC 6.2.1.1] effects this uptake of acetate.
J Gen Microbiol 1977 Oct
PMID:The enzymic interconversion of acetate and acetyl-coenzyme A in Escherichia coli. 2 41

Nitrogen fixation (Nif)-derepressed mutants of Klebsiella pneumoniae consumed, under optimum conditions, 7.5 to 8.5 mol glucose per mol N2 fixed. The nitrogenase system of these mutants catalysed the production of about 1.3 mol H2 per mol N2 reduced. Almost one-third of the energy as ATP and reductant used by nitrogenase in vivo may be lost in H2 production, since an ATP/2e ratio of approximately 4 was obtained. Nitrogenase-catalysed H2 production was not substantially suppressed by increasing the partial pressure of N2 from 0.2 atm (20 kPa) to 1 atm (101 kPa). In the absence of N2, H2 production catalysed by nitrogenase increased about threefold. It is concluded that nitrogenase-catalysed H2 production is of major importance in the overall efficiency of biological N2 fixation in vivo.
J Gen Microbiol 1977 Nov
PMID:Energetics of biological nitrogen fixation: determination of the ratio of formation of H2 to NH4+ catalysed by nitrogenase of Klebsiella pneumoniae in vivo. 2 79

Determinants of 45Ca influx, 45Ca efflux, and 22Na efflux were examined in dog red blood cells. 45Ca influx is strongly influenced by the Na concentration on either side of the membrane, being stimulated by intracellular Na and inhibited by extracellular Na. A saturation curve is obtained when Ca influx is plotted as a function of medium Ca concentration. The maximum Ca influx is a function of pH (increasing with greater alkalinity) and cell volume (increasing with cell swelling). Quinidine strongly inhibits Ca influx. Efflux of 45Ca is stimulated by increasing concentrations of extracellular Na. 22Na efflux is stimulated by either Ca or Na in the medium, and the effects of the two ions are mutually exclusive rather than additive. Quinidine inhibits Ca-activated 22Na efflux. The results are considered in terms of a model for Ca-Na exchange, and it is concluded that the system shows many features of such a coupled ion transport system. However, the stoichiometric ratio between Ca influx and Ca-dependent Na efflux is highly variable under different experimental conditions. Because the Ca fluxes may reflect a combination of ATP-dependent, outward transport and Na-linked passive movements, the true stoichiometry of an exchanger may not be ascertainable in the absence of a specific Ca pump inhibitor. The meaning of these observations for Ca-dependent volume regulation by dog red blood cells is discussed.
J Gen Physiol 1978 Jan
PMID:Sodium and calcium movements in dog red blood cells. 2 6

Uptake of choline, a structural component of pneumococcal C- and F-teichoic acids, into bacteria growing in a defined medium was very efficient with an uptake constant ([S]10 5) of 3.2 microns. It was inhibited by iodoacetate, dinitrophenol and oligomycin but not by structural analogues of choline. Ethanolamine, however, was transported in the absence of choline but with a reduced affinity ([S]0.5 71.4 microns). The same constitutive system was probably used by both ethanolamine and choline. It is suggested that this system required ATP and probably involved choline kinase.
J Gen Microbiol 1978 Dec
PMID:The uptake of choline by Streptococcus pneumoniae. 3 10

At an external pH of 3.5, nigericin (which catalyses an electroneutral H+/K+ exchange) abolished the transmembrane proton gradient (delta pH) of Bacillus acidocaldarius, causing a rapid acidification of the cytoplasm from approximately pH 6.0 to pH 3.5. A pronounced loss of viability and fine-structural changes rapidly followed treatment with nigericin. A marked decline in respiration and an even more rapid decrease in cytoplasmic ATP were observed. Activity of at least one cytoplasmic enzyme decreased more slowly. There was no generalized loss in the integrity of the cytoplasmic membrane, as assayed by permeability to inulin or Na+ or by release of ultraviolet light-absorbing compounds. The loss of viability upon treatment with carbonyl cyanide m-chlorophenylhydrazone was similar to what observed with nigericin, so proton influx alone, rather than together with K+ efflux, was probably involved in the death of the organism. Moreover, acidification of the cytoplasm rather than abolition of the delta pH was the lethal event, since no loss of viability was observed when the delta pH was abolished by elevation of the external pH.
J Gen Microbiol 1979 Sep
PMID:Nigericin-induced death of an acidophilic bacterium. 4 67

Using gel filtration chromatography, we find a single peak of deoxythymidine phosphorylating activity in Chlamydomonas reinhardti. This activity has characteristics of a thymidine kinase, in that (1) it will utilize ATP (or dATP) or CTP (or dCTP) as phosphoryl donor, but not AMP or phenyl phosphate, and (2) it is inhibited by dTTP (and less so by dTDP, dUTP, and dUDP) but is unaffected by 3'-5' cyclic AMP. Partially purified chlamydomonas thymidine kinase has a pH optimum near 8.5, and a molecular weight of 80,000 to 85,000 daltons. Kinetic studies indicate a ping-pong mechanism with a Km for thymidine of 1.5 x 10(-7) moles per liter. 5-Bromo- and 5-fluorodeoxyuridine, and to a lesser degree deoxyuridine, are competitive inhibitors, but significant phosphorylation of these nucleotides could not be demonstrated in vitro by thymidine kinase. While thymidine is phosphorylated to dTMP by crude Chlamydomonas extracts, greater than 80% of the product formed by the partially purified enzyme is dTTP. Further, the gel filtration elution position of the single deoxythymidylate kinase activity present in cell extracts coincides with that of thymidine kinase. These results suggest that a multifunctional enzyme, rather than three separate phosphorylating activities, may be responsible for dTTP formation.
Mol Gen Genet 1979 Nov
PMID:Characterization of thymidine kinase and phosphorylation of deoxyribonucleosides in Chlamydomonas reinhardti. 4 38

The biochemical explanation for lipid accumulation was investigated principally in Candida 107 and, for comparison, in the non-oleaginous yeast Candida utilis. There were no significant differences between these two yeasts in their control of glucose uptake; in both yeasts, the rates of glucose uptake were independent of the growth rate and were higher in carbon-limited chemostat cultures than in nitrogen-limited cultures. There was no lipid turnover in either yeast, as judged from [14C]acetate uptake and subsequent loss of 14C from the lipid of steady-state chemostat cultures. Acetyl-CoA carboxylase from both yeasts was similar in most characteristics except that from Candida 107 was activated by citrate (40% activation at 1 mM). The enzyme from Candida 107 was relatively unstable and, when isolated from nitrogen-limited (lipid-accumulating) cultures, was accompanied by a low molecular weight inhibitor. The reason for lipid accumulation is attributed to the decrease in the intracellular concentration of AMP as cultures become depleted of nitrogen. As the NAD+-dependent isocitrate dehydrogenase of Candida 107, but not C. utilis, requires AMP for activity, the metabolism of citrate through the tricarboxylic acid cycle in the mitochondria becomes arrested. In Candida 107, but not in C. utilis, there is an active ATP:citrate lyase which converts the accumulating citrate, when it passes into the cytosol, into acetyl-CoA and oxaloacetate. The former product is then available for fatty acid biosynthesis which is stimulated by the high ATP concentration within the cells, by the activation of acetyl-CoA carboxylase by citrate and by the provision of NADPH generated as oxaloacetate is converted via malate to pyruvate. Similar characteristics were evident in oleaginous strains of Rhodotorula glutinis and Mucor circinelloides but not in non-oleaginous representatives of these species.
J Gen Microbiol 1979 Oct
PMID:A biochemical explanation for lipid accumulation in Candida 107 and other oleaginous micro-organisms. 4 15


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