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)

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

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

Pathways of ammonia assimilation into glutamic acid in Bacillus azotofixans, a recently characterized nitrogen-fixing species of Bacillus, were investigated through observation by NMR spectroscopy of in vivo incorporation of 15N into glutamine and glutamic acid in the absence and presence of inhibitors of ammonia-assimilating enzymes, in combination with measurements of the specific activities of glutamate dehydrogenase, glutamine synthetase, glutamate synthase, and alanine dehydrogenase. In ammonia-grown cells, both the glutamine synthetase/glutamate synthase and the glutamate dehydrogenase pathways contribute to the assimilation of ammonia into glutamic acid. In nitrate-grown and nitrogen-fixing cells, the glutamine synthetase/glutamate synthase pathway was found to be predominant. NADPH-dependent glutamate dehydrogenase activity was detectable at low levels only in ammonia-grown and glutamate-grown cells. Thus, B. azotofixans differs from Bacillus polymyxa and Bacillus macerans, but resembles other N2-fixing prokaryotes studied previously, as to the pathway of ammonia assimilation during ammonia limitation. Implications of the results for an emerging pattern of ammonia assimilation by alternative pathways among nitrogen-fixing prokaryotes are discussed, as well as the utility of 15N NMR for measuring in vivo glutamate synthase activity in the cell.
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PMID:Glutamate biosynthesis in Bacillus azotofixans. 15N NMR and enzymatic studies. 289 94

Reduced pyridine nucleotide dependent glutamate synthase [L-glutamate: NADP+ oxidoreductase (transaminating); EC 1.4.1.13] was purified to homogeneity from Bacillus subtilis PCI 219. The molecular weight of the enzyme was 210,000, and the enzyme was composed of two nonidentical subunits with molecular weights of 160,000 and 56,000. The absorption and CD spectra of the enzyme indicated that the enzyme is an iron-sulfur flavoprotein. The enzyme was found to contain 1:1:7.4:8.7 mol of FMN, FAD, iron atoms, and acid-labile sulfur atoms per mol (MW 210,000). EPR measurements of the NADPH-reduced enzyme at 77K revealed the formation of a stable flavin semiquinone intermediate; however, none of the signals originating from the iron-sulfur cluster was observed. Still at 4.2K the EPR signals in the region of g = 2, which may originate from the paramagnetic iron-sulfur cluster, were clearly observed for both the isolated and dithionite-reduced states of the enzyme. The enzyme exhibited a wide coenzyme specificity, and either NADPH or NADH could be used as electron donor, although the latter was less effective. The enzyme activity was also expressed when ammonium chloride was substituted for L-glutamine. The optimum pHs for NADPH-Gln-, NADH-Gln-, and NADPH-NH3-dependent reactions were 7.8, 6.9, and 9.4, respectively. The apoenzyme exhibited substantial inactivation of the Gln-dependent activities but still retained the NH3-dependent activities. Enzyme reduction-oxidation experiments, initial velocity experiments, and product inhibition patterns revealed that both the NADPH-Gln- and NADH-Gln-dependent reactions coincided with the two-site ping-pong uni-uni bi-bi kinetic mechanism, while the NADPH-NH3-dependent reaction deviated from Michaelis-Menten kinetics. The Gln-dependent activities were inhibited by several TCA cycle members, especially L-malate and fumarate, as well as L-methionine-SR-sulfoximine, pyridoxal-5'-phosphate, and pCMB. The regulation of the glutamate synthase, glutamine synthetase [EC 6.3.1.2], and glutamate dehydrogenase [EC 1.4.1.3] activities was examined with cultures of cells grown with various nitrogen and carbon sources.
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PMID:Glutamate synthase from Bacillus subtilis PCI 219. 301 66

The central role of NH4+-assimilation in the microbial metabolization of several inorganic nitrogen sources and the regulation of its key enzymes--glutamate dehydrogenases (GDH--EC 1.4.1.2. and EC 1.4.1.4.), glutamine synthetase (GS--EC 6.3.1.2.) and glutamate synthase (GOGAT--EC 1.4.1.3.)--are presented. In excess of ammonia gramnegative bacteria as well as yeasts assimilate this ion in a NADH + H+ or NADPH + H+ dependent reaction by GDH. Under NH4+-limitation--in natural environments rather the rule than the exception--the ammonia assimilation is ATP dependent and catalyzed via GS and GOGAT. Subsequently the connection between the nitrogen metabolization and the resulting changes in the extracellular pH of growing yeast cultures is discussed. The stoichiometric exchange between NH4+ and H+ led to the assumption that in the physiological pH-range an energy dependent NH4+/H+ transport is the preferred++ mechanism of ammonia uptake for NH4+ excess as well as for NH4+ shortage.
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PMID:[Nitrogen regulation in microorganisms]. 305 85

The literature concerning the metabolism of carbon and nitrogen compounds in ectomycorrhizal associations of trees is reviewed. The absorption and translocation of mineral ions by the mycelia require an energy source and a reductant which are both supplied by respiratory catabolism of carbohydrates produced by the host plant. Photosynthates are also required to generate the carbon skeletons for amino acid and carbohydrate syntheses during the growth of the mycelia. Competition for photosynthates occurs between the fungal cells and the various vegetative sinks in the host tree. The nature of carbon compounds involved in these processes, their routes of metabolism, the mechanisms of control and the partitioning of metabolites between the various sites of utilization are only poorly understood. Both ascomycetous and basidiomycetous ectomycorrhizal fungi synthesize and some, if not all, accumulate mannitol, trehalose and triglycerides. The fungal strains employ the Embden--Meyerhof pathway of glucose catabolism and the key enzymes of the pentose phosphate pathway (6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, transaldolase and transketolase). Anaplerotic CO2 fixation, via pyruvate carboxylase and/or phosphoenolpyruvate carboxykinase, provides high pools of amino acids. This process could be important in the recapture and assimilation of respired CO2 in the rhizosphere. The ectomycorrhizas are thought to contain the Embden--Meyerhof pathway, the pentose phosphate pathway and the tricarboxylic acid cycle, which provide the carbon skeletons for the assimilation of ammonia into amino acids. The main route of assimilation of ammonia appears to be through the glutamine synthetase-glutamate synthase cycle in the ectomycorrhizas. Glutamate dehydrogenase plays a minor role in this process. Glutamate dehydrogenase and glutamine synthetase are present in free-living ectomycorrhizal fungi and they participate in the assimilation of ammonia and the synthesis of amino acids through the glutamate dehydrogenase/glutamine synthetase sequence. In both in vitro cultures of fungi and ectomycorrhizas, the assimilated nitrogen accumulates in glutamine. Glutamine, but also ammonia, are thought to be exported from the fungal tissues to the host cells. Studies on the metabolism of ectomycorrhizas and ectomycorrhizal fungi have focused on the metabolic pathways and compounds which accumulate in the symbiotic tissues. Studies on regulation of the overall process, and the control of enzyme activity in particular, are still fragmentary.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Carbon and nitrogen metabolism in ectomycorrhizal fungi and ectomycorrhizas. 312 Jul 92

The effect of the mutation of threonine and homoserine resistance (thrr) on the activity of the enzymes catalysing the biosynthesis of glutamic acid, glutamate synthase (EC 1.4.1.13) and glutamate dehydrogenase (EC 1.4.1.4), and on the productivity of a threonine-producing E. coli strain obtained by gene engineering was being studied. The resistance to threonine was found to correlate well with the increasing activities of the abovementioned enzymes and with a higher productivity of the E. coli strain.
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PMID:[Amination in E. coli strains effectively producing threonine]. 393 95

Treatment of cell suspension cultures of Phaseolus vulgaris c.v. Immuna with an elicitor preparation heat-released from the cell walls of the phytopathogenic fungus Colletotrichum lindemuthianum resulted in rapid accumulation of the prenylated 5-hydroxyisoflavanone phytoalexin kievitone followed by later accumulation of the pterocarpan-derived phytoalexin phaseollin. Kievitone formation was preceded by rapid transient increases in the extractable activities of the enzymes L-phenylalanine ammonia-lyase and chalcone synthase. The extractable activities of 15 enzymes were measured in the cell cultures during the period of kievitone accumulation. The results suggest a highly selective induction of enzymes associated directly with the phytoalexin pathway. No induction of enzymes of pathways diverging from or providing substrates for the phenylpropanoid----isoflavonoid pathway was observed. The increase in glutamate dehydrogenase activity in control cultures was prevented by elicitor application. A comparison of enzyme activities in control and Colletotrichum-infected bean hypocotyls provided further evidence of the selective induction of enzymes of phytoalexin synthesis, although peroxidase, glutamate dehydrogenase and glutamate synthase activities were higher in infected than in healthy hypocotyls. It is concluded that the major enzymic changes occurring in elicitor-treated bean cells are probably those directly associated with defence mechanisms such as the formation of isoflavonoid phytoalexins (this paper) or accumulation of phenolic compounds and hydroxyproline-protein in the cell walls [Bolwell, G. P. et al. (1985) Eur. J. Biochem. 148, 571-578].
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PMID:Metabolic changes in elicitor-treated bean cells. Selectivity of enzyme induction in relation to phytoalexin accumulation. 399 94

At least two pathways exist in Klebsiella aerogenes for glutamate synthesis. A mutant blocked in one pathway due to the loss of glutamate dehydrogenase (gltD) does not require glutamate and has the same growth characteristics as the parent strain in most media; however, its growth is inhibited by the analogues methionine sulfoximine and methionine sulfone. Wild-type Klebsiella is resistant to 0.1 M methionine sulfoximine or methionine sulfone, whereas the gltD mutant is sensitive to 1 mM concentrations. Either glutamate or glutamine is effective in overcoming this inhibition. Activities of both glutamine synthetase and glutamate synthetase, two enzymes involved in the second pathway of glutamate synthesis, are inhibited by methionine sulfoximine and methionine sulfone. The primary effect of methionine sulfoximine appears to be the prevention of glutamine production necessary for subsequent glutamate synthesis via glutamate synthetase enzyme.
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PMID:Effect of methionine sulfoximine and methionine sulfone on glutamate synthesis in Klebsiella aerogenes. 414 97


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