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)

ATP and glutamine are the sources of endogenous ammonia in rat brain synaptosomes. The amount of endogenous ammonia formed from exogenous ATP is not sufficient to assure the maximum rate of aspartate and glutamate accumulation in the synaptosomes utilizing pyruvate + malate. Addition of exogenous NH4+ or depolarization of synaptosome plasma membranes with high K+ concentration led to a twofold increase in the rate of accumulation of these amino acids. This indicates that both exogenous and endogenous NH4+ is involved in the synthesis of aspartate and glutamate in nerve terminals. Accumulation of glutamate was stimulated by aminooxyacetate and inhibited by haloperidol which indicates that NH4+ is bound in the reaction catalysed by glutamate dehydrogenase. Endogenous oxaloacetate derived from pyruvate metabolism was the substrate for synthesis of aspartate. Additive inhibition of aspartate accumulation by fluorocitrate and (-) hydroxyacetate shows that, in addition to the tricarboxylic acid cycle, the reaction catalysed by ATP-citrate lyase serves in the synaptosomes as another source of oxaloacetate.
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PMID:Synthesis of glutamate and aspartate in rat brain synaptosomes. 288 15

Activity of L-amino acid oxidases was studied using several procedures. Optimal concentrations of L-lysine-alpha-oxidase, suitable for each procedure, were established involving highly purified preparations of the enzyme from Trichoderma sp. Estimation of the enzymatic activity carried out by means of calculation of the reduced cofactor accumulated led to two-fold exceeding of the results. The most sensitive procedure was based on evaluation of ammonium content in the reaction catalyzed by glutamate dehydrogenase and the procedure where peroxidase and o-dianizidine were used.
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PMID:[Determination of L-amino acid oxidase activity]. 288 70

Pathways of ammonia assimilation into glutamic acid and alanine in Bacillus polymyxa were investigated by 15N NMR spectroscopy in combination with measurements of the specific activities of glutamate dehydrogenase, glutamine synthetase, glutamate synthetase, alanine dehydrogenase, and glutamic-alanine transaminase. Ammonia was found to be assimilated into glutamic acid predominantly by NADPH-dependent glutamate dehydrogenase with a Km of 2.9 mM for NH4+ not only in ammonia-grown cells but also in nitrate-grown and nitrogen-fixing cells in which the intracellular NH4+ concentrations were 11.2, 1.04, and 1.5 mM, respectively. In ammonia-grown cells, the specific activity of alanine dehydrogenase was higher than that of glutamic-alanine transaminase, but the glutamate dehydrogenase/glutamic-alanine transaminase pathway was found to be the major pathway of 15NH4+ assimilation into [15N]alanine. The in vitro specific activities of glutamate dehydrogenase and glutamine synthetase, which represent the rates of synthesis of glutamic acid and glutamine, respectively, in the presence of enzyme-saturating concentrations of substrates and coenzymes are compared with the in vivo rates of biosynthesis of [15N]glutamic acid and [alpha,gamma-15N]glutamine observed by NMR, and implications of the results for factors limiting the rates of their biosynthesis in ammonia- and nitrate-grown cells are discussed.
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PMID:Ammonia assimilation in Bacillus polymyxa. 15N NMR and enzymatic studies. 288 2

The specific activities of glutamine synthetase (GS) and glutamate synthase (GOGAT) were 4.2- and 2.2-fold higher, respectively, in cells of Azospirillum brasilense grown with N2 than with 43 mM NH4+ as the source of nitrogen. Conversely, the specific activity of glutamate dehydrogenase (GDH) was 2.7-fold higher in 43 mM NH4+-grown cells than in N2-grown cells. These results indicate that NH4+ could be assimilated and that glutamate could be formed by either the GS-GOGAT or GDH pathway or both, depending on the cellular concentration of NH4+. The routes of in vivo synthesis of glutamate were identified by using 13N as a metabolic tracer. The products of assimilation of 13NH4+ were, in order of decreasing radioactivity, glutamine, glutamate, and alanine. The formation of [13N]glutamine and [13N]glutamate by NH4+-grown cells was inhibited in the additional presence of methionine sulfoximine (an inhibitor of GS) and diazooxonorleucine (an inhibitor of GOGAT). Incorporation of 13N into glutamine, glutamate, and alanine decreased in parallel in the presence of carrier NH4+. These results imply that the GS-GOGAT pathway is the primary route of NH4+ assimilation by A. brasilense grown with excess or limiting nitrogen and that GDH has, at best, a minor role in the synthesis of glutamate.
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PMID:Assimilation of 13NH4+ by Azospirillum brasilense grown under nitrogen limitation and excess. 288 45

Pathways of ammonia assimilation into glutamic acid in Bacillus macerans were investigated by measurements of the specific activities of glutamate dehydrogenase (GDH), glutamine synthetase, and glutamate synthase. In ammonia-rich medium, GDH was the predominant pathway of ammonia assimilation. In nitrogen-fixing cells in which the intracellular NH4+ concentration was 1.4 +/- 0.5 mM, the activity of GDH with a Km of 2.2 mM for NH4+ was found to be severalfold higher than that of glutamate synthase. The result suggests that GDH plays a significant role in the assimilation of NH4+ in N2-fixing B. macerans.
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PMID:Role of glutamate dehydrogenase in ammonia assimilation in nitrogen-fixing Bacillus macerans. 288 50

Glutamate dehydrogenase (aminating) and glutamine synthetase activities were assayed in Mycobacterium smegmatis following growth on various carbon and nitrogen sources. The activities (expressed as nmoles product formed/min/mg crude extract protein) of these two enzymes were higher in crude extracts from glucose-grown cells than in glycerol- or fructose-grown cells. In the presence of succinate, pyruvate, fumarate or acetate in the growth medium, both these enzyme activities were lower than those in citrate-grown cells. The glutamate dehydrogenase (GDH) activity was the same in asparagine and glutamine-grown cells. Ammonium chloride, alanine or glutamic acid, when used as nitrogen source, resulted in low GDH activity as compared to asparagine-grown cells. Glutamine synthetase activity was considerably lower (2-4 fold) when the cells were grown on alanine, glutamine, glutamic acid or ammonium chloride as the nitrogen source than those in asparagine-grown cells. Glutamate and ammonium chloride, when present in the growth medium, repressed both glutamate dehydrogenase and glutamine synthetase, though the degree of repression was small. The results suggest that only a weak transcriptional control operates for these enzyme activities in M. smegmatis.
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PMID:Changes in the enzyme activities involved in nitrogen assimilation in Mycobacterium smegmatis under various growth conditions. 289 60

2-Keto-3-fluoroglutaric acid prepared by acid hydrolysis of its diethyl ester is stable, as the free acid in aqueous solution at pH 2, and can be stored at -20 degrees C for several years. Both enantiomers are reduced by NADH in the presence of glutamate dehydrogenase (EC 1.4.1.2) to the two diastereomers of 3-fluoro-L-glutamate, which are stable at neutral pH and at high pH unless heated. 2-Keto-3-fluoroglutarate exists in solution almost entirely as a hydrate both at low and neutral pH. Both enantiomers of ketofluoroglutarate react with the pyridoxamine forms of aspartate, alanine and 4-aminobutyrate transaminases to give fluoride release. 2 mol of cosubstrate amino acid react for each mol of ketofluoroglutarate (KFG) when starting from the pyridoxamine form of the enzyme: 2 RCHNH2COOH + KFG + H2O----F- + NH4+ + glutamate + 2 RCOCOOH. Both diastereomers of fluoroglutamate are decarboxylated by glutamate decarboxylase (EC 4.1.1.15) with fluoride release: KFG + H2O----CO2 + F- + HCOCH2CH2COOH. By contrast, only one isomer of fluoroglutamate will react with the pyridoxal form of glutamate-oxalacetate transaminase to give fluoride release: HOOCCHNH2CHFCH2COOH + H2O----4F- + NH4+ + HOOCCOCH2CH2COOH. The enzymatic decarboxylation of 3-fluoroisocitrate produces only one enantiomer of ketofluoroglutarate, which is reduced to threo (2R,3R)-3-fluoroglutamate by NADH and glutamate dehydrogenase: [2R,3S]-HOOCCH(OH)CF(COOH)CH2COOH + NADP+----[3R]-KFG + CO2 + NADPH + H+. The proton, 13C, and 19F-NMR parameters of ketofluoroglutarate and the two fluoroglutamate diastereomers are presented. These molecules are useful probes of enzymatic mechanisms thought to involve carbanion intermediates.
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PMID:2-Keto-3-fluoroglutarate: a useful mechanistic probe of 2-keto-glutarate-dependent enzyme systems. 289 78

Evidence from in vitro and in vivo studies showed that in Rhizobium phaseoli ammonium is assimilated by the glutamine synthetase (GS)-glutamate synthase NADPH pathway. No glutamate dehydrogenase activity was detected. R. phaseoli has two GS enzymes, as do other rhizobia. The two GS activities are regulated on the basis of the requirement for low (GSI) or high (GSII) ammonium assimilation. When the 2-oxoglutarate/glutamine ratio decreases, GSI is adenylylated. When GSI is inactivated, GSII is induced. However, induction of GSII activity varied depending on the rate of change of this ratio. GSII was inactivated after the addition of high ammonium concentrations, when the 2-oxoglutarate/glutamine ratio decreased rapidly. Ammonium inactivation resulted in alteration of the catalytic and physical properties of GSII. GSII inactivation was not relieved by shifting of the cultures to glutamate. After GSII inactivation, ammonium was excreted into the medium. Glutamate synthase activity was inhibited by some organic acids and repressed when cells were grown with glutamate as the nitrogen source.
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PMID:Ammonium assimilation in Rhizobium phaseoli by the glutamine synthetase-glutamate synthase pathway. 289 29

Rhizobium phaseoli lacks glutamate dehydrogenase (GDH) and assimilates ammonium by the glutamine synthetase-glutamate synthase pathway. A strain of R. phaseoli harboring the Escherichia coli GDH structural gene (gdhA) was constructed. GDH activity was expressed in R. phaseoli in the free-living state and in symbiosis. Nodules with bacteroids that expressed GDH activity had severe impairment of nitrogen fixation. Also, R. phaseoli cells that lost GDH activity and assimilated ammonium by the glutamine synthetase-glutamate synthase pathway preferentially nodulated Phaseolus vulgaris.
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PMID:Introduction of the Escherichia coli gdhA gene into Rhizobium phaseoli: effect on nitrogen fixation. 289 30

The activities of citrate synthase (EC 4.1.3.7) and NADP+-dependent glutamate dehydrogenase (GDH) (EC 1.4.1.4) of Saccharomyces cerevisiae were inhibited in vitro by glyoxylate. In the presence of glyoxylate, pyruvate and glyoxylate pools increased, suggesting that glyoxylate was efficiently transported and catabolized. Pyruvate accumulation also indicates that citrate synthase was inhibited. A decrease in the glutamate pool was also observed under these conditions. This can be attributed to an increased transamination rate and to the inhibitory effect of glyoxylate on NADP+-dependent GDH. Furthermore, the increase in the ammonium pool in the presence of glyoxylate suggests that NADP+-dependent GDH was being inhibited in vivo, since the activity of glutamine synthetase did not decrease under these conditions. We propose that the inhibition of both citrate synthase and NADP+-dependent GDH could form part of a mechanism that regulates the internal 2-oxoglutarate concentration.
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PMID:Coordinated regulation of ammonium assimilation and carbon catabolism by glyoxylate in Saccharomyces cerevisiae. 289 26


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