Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.4.1.2 (glutamate dehydrogenase)
4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A mutant of Klebsiella aerogenes lacking glutamate synthase activity (asm-200) is blocked in only one pathway of glutamate synthesis and can still use glutamate dehydrogenase to produce glutamate when ammonia in sufficient concentration, i.e., higher than 1 mM, is provided in the medium. However, a mutant that has neither glutamate synthase nor glutamate dehydrogenase activities (asm-200, gdhD1) requires glutamate. Transductants obtained by phage grown on wild-type cells of this double mutant, selected on medium containing less than 1 mM ammonia, regain glutamate synthase but not glutamate dehydrogenase. Surprisingly, these gdhD1 transductants grow as well in a variety of media as does a strain with glutamate dehydrogenase activity. Furthermore, transductions with these and other mutants indicate that the genes encoding glutamate synthase, glutamate dehydrogenase, glutamine synthetase, and citrate synthase are not closely linked.
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PMID:Mutants of Klebsiella aerogenes lacking glutamate dehydrogenase. 414 14

Methionine sulfoximine inhibits the growth of Salmonella typhimurium at a concentration of 50 muM, and the addition of glutamine, but not glutamate, is sufficient to overcome this inhibition. The analogue causes 50% inhibition of glutamine synthetase activity at 2 to 4 muM and of glutamate synthase at 2 to 3 mM when these enzymes are assayed in vitro. No inhibition of glutamate dehydrogenase activity is observed at analogue concentrations as high as 50 mM. Two mutants selected for their resistance to methionine sulfoximine inhibition have a partial growth requirement for glutamine and a reduction in the glutamine synthetase and glutamate synthase activities. The sensitivity of the remaining glutamine synthetase activity in these mutants to methionine sulfoximine inhibition appears unaltered, and the lesions conferring the analogue resistance may not affect glutamine synthetase directly.
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PMID:Characterization of Salmonella typhimurium strains sensitive and resistant to methionine sulfoximine. 415 9

A reduced nicotinamide adenine dinucleotide (NADH)-dependent glutamate synthase has been detected and partially purified from crude extracts of Saccharomyces cerevisiae. The enzyme is specific for NADH, glutamine, and alpha-ketoglutarate (K(m) values of 2.6 muM, 1.0 mM, and 140 muM, respectively) and has a pH optimum between 7.1 and 7.7. The stoichiometry of the reaction has been determined as 2 mol of glutamate synthesized per mol of glutamine consumed. Glutamate synthase can be distinguished from either of the glutamate dehydrogenases of yeast on the basis of its substrate requirements and behavior during agarose gel and ion exchange chromatography. Variations in the specific activity of glutamate synthase, which occur in response to changes in the growth medium, are similar in character to those observed with the nicotinamide adenine dinucleotide phosphate-dependent (anabolic) glutamate dehydrogenase.
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PMID:Glutamate synthase: properties of the reduced nicotinamide adenine dinucleotide-dependent enzyme from Saccharomyces cerevisiae. 436 65

The effect of cAMP on the intracellular levels of five enzymes concerned with the interconversion of glutamate and glutamine in E. coli has been examined. Cyclic AMP added to the culture medium increases the levels of glutamate dehydrogenase (EC 1.4.1.4) and glutamine synthetase (EC 6.3.1.2); it decreases the levels of glutamate synthase (EC 1.4.1.X), and glutaminase A (EC 3.5.1.2). Cyclic AMP did not affect the level of glutaminase B (EC 3.5.1.2). These alterations in enzyme levels by cAMP require cyclic AMP receptor protein, since the levels of these enzymes were unchanged by cAMP in a mutant lacking this receptor. Chloramphenicol also abolished the effects of cAMP, a result that implies protein synthesis is necessary for these changes in enzyme levels to occur. The reciprocal effects of cAMP on the levels of these enzymes may play an important role in the cellular regulation of nitrogen metabolism.
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PMID:Adenosine 3':5'-cyclic monophosphate control of the enzymes of glutamine metabolism in Escherichia coli. 440 45

Selenomonas ruminantium was found to possess two pathways for NH4+ assimilation that resulted in net glutamate synthesis. One pathway fixed NH4+ through the action of an NADPH-linked glutamate dehydrogenase (GDH). Maximal GDH activity required KCl (about 0.48 M), but a variety of monovalent salts could replace KCl. Complete substrate saturation of the enzyme by NH4+ did not occur, and apparent Km values of 6.7 and 23 mM were estimated. Also, an NADH-linked GDH activity was observed but was not stimulated by KCl. Cells grown in media containing non-growth-rate-limiting concentrations of NH4+ had the highest levels of GDH activity. The second pathway fixed NH4+ into the amide of glutamine by an ATP-dependent glutamine synthetase (GS). The GS did not display gamma-glutamyl transferase activity, and no evidence for an adenylylation/deadenylylation control mechanism was detected. GS activity was highest in cells grown under nitrogen limitation. Net glutamate synthesis from glutamine was effected by glutamate synthase activity (GOGAT). The GOGAT activity was reductant dependent, and maximal activity occurred with dithionite-reduced methyl viologen as the source of electrons, although NADPH or NADH could partially replace this artificial donor system. Flavin adenine dinucleotide, flavin mononucleotide, or ferredoxin could not replace methyl viologen. GOGAT activity was maximal in cells grown with NH4+ as sole nitrogen source and decreased in media containing Casamino Acids.
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PMID:Ammonia assimilation and glutamate formation in the anaerobe Selenomonas ruminantium. 610 49

The ability of Streptococcus mutans to synthesize amino acids was examined. A total of 8 of 12 laboratory strains grew anaerobically on solid-defined medium that contained no amino acids. Several isolates, therefore, assimilated ammonia for the biosynthesis of amino acids. These strains included representatives of five serotypes. One strain, DR0001, was also grown in liquid-defined medium. The enzymes of two pathways by which ammonia can be fixed were detected in this strain DR0001 could use either a reduced nicotinamide adenine dinucleotide phosphate-coupled glutamate dehydrogenase or the combined action of adenosine 5'-triphosphate-driven glutamine synthetase with a reduced nicotinamide adenine dinucleotide-coupled glutamate synthase to assimilate ammonia for the biosynthesis of amino acids. Evidence that both pathways were functional was provided by an analysis of the influence of the nitrogen source on enzyme levels and by the isolation and characterization of glutamate dehydrogenase-negative mutants.
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PMID:Regulation and function of ammonia-assimilating enzymes in Streptococcus mutans. 610 77

Ammonium ions were incorporated into L-glutamate and alpha-ketoglutarate in epimastigote forms of Trypanosoma cruzi through the following enzymatic systems: NADPH and NADH-dependent glutamate dehydrogenase, NADPH-dependent glutamate synthase, L-glutamine synthetase and NADH-dependent glutamate synthase in order of decreasing specific activity (mumoles of product formed/min/mg protein). The pH optima and Km's for the glutamate dehydrogenase system were determined. Disc electrophoresis showed the presence of cathodic bands of GDH activity, which were highly dependent on NADP+.
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PMID:Incorporation of ammonium in amino acids by Trypanosoma cruzi. 610 92

We have characterized a mutant of Rhizobium meliloti strain 2011 which cannot use ammonium as a nitrogen source. This mutant, RTm2620, was found to have significantly altered glutamate synthase activity. Both the mutant and the wild-type strains had glutamate dehydrogenase activity, which, although stimulated in the presence of glutamate and ammonium, was apparently insufficient to allow ammonium assimmilation. We conclude that the glutamine synthetase-glutamate synthase pathway may be the normal mode of ammonium assimilation by this strain in the free-living state. Independent revertants of Rm2620 were isolated and fell into two classes. Class I revertants regained partial glutamate synthase activity and had the same levels of glutamate dehydrogenase activity as Rm2620. Class II revertants retained the altered glutamate synthase activity but acquired a very high level of assimilatory glutamate dehydrogenase activity. Both classes were found to be altered in their symbiotic properties, although the original Rm2620 mutant was normal in this regard.
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PMID:Ammonium assimilation in Rhizobium meliloti. 610 11

Mutant strains SU1, SU4, and US1 lacking glutamate synthase (GOGAT) activity were isolated from strains of P. aeruginosa for which histidine is a growth rate-limiting source of nitrogen. Strains SU1 and SU4 were unable to grow when a low concentration of ammonia and a variety of compounds, including histidine, were supplied as sole sources of nitrogen. A revertant of strain SU1, strain 39, produced no GOGAT but high levels of nicotinamide adenine dinucleotide-dependent glutamate dehydrogenase and had restored ability to grow on a limited number of nitrogen sources. Strain US1 grew at the same rate in histidine medium as did its parent; it was derepressed for glutamine synthase synthesis, and histidase was less sensitive to repression by ammonia than in the parent strain. We conclude that GOGAT is not essential for growth on histidine but high levels of glutamine synthase are required nd high levels of nicotinamide adenine dinucleotide-dependent glutamate dehydrogenase can sustain growth at low concentrations of ammonia in the absence of GOGAT.
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PMID:Growth of Pseudomonas aeruginosa mutants lacking glutamate synthase activity. 611 33

Urease and glutamine synthetase activities in Selenomonas ruminantium strain D were highest in cells grown in ammonia-limited, linear-growth cultures or when certain compounds other than ammonia served as the nitrogen source and limited the growth rate in batch cultures. Glutamate dehydrogenase activity was highest during glucose (energy)-limited growth or when ammonia was not growth limiting. A positive correlation (R = 0.96) between glutamine synthetase and urease activities was observed for a variety of growth conditions, and both enzyme activities were simultaneously repressed when excess ammonia was added to ammonia-limited, linear-growth cultures. The glutamate analog methionine sulfoximine (MSX), inhibited glutamine synthetase activity in vitro, but glutamate dehydrogenase, glutamate synthase, and urease activities were not affected. The addition of MSX (0.1 to 100 mM) to cultures growing with 20 mM ammonia resulted in growth rate inhibition that was dependent upon the concentration of MSX and was overcome by glutamine addition. Urease activity in MSX-inhibited cultures was increased significantly, suggesting that ammonia was not the direct repressor of urease activity. In ammonia-limited, linear-growth cultures, MSX addition resulted in growth inhibition, a decrease in GS activity, and an increase in urease activity. These results are discussed with respect to the importance of glutamine synthetase and glutamate dehydrogenase for ammonia assimilation under different growth conditions and the relationship of these enzymes to urease.
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PMID:Regulation of urease and ammonia assimilatory enzymes in Selenomonas ruminantium. 611 7


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