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:1.4.3.11 (glutamate dehydrogenase)
4,437 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glutamine synthetase (EC 6.3.1.2) was localized within the matrix compartment of avian liver mitochondria. The submitochondrial localization of this enzyme was determined by the digitonin-Lubrol method of Schnaitman and Greenawalt (35). The matrix fraction contained over 74% of the glutamine synthetase activity and the major proportion of the matirx marker enzymes, malate dehydrogenase (71%), NADP-dependent isocitrate dehydrogenase (83%), and glutamate dehydrogenase (57%). The highest specific activities of these enzymes were also found in the matrix compartment. Oxidation of glutamine by avian liver mitochondria was substantially less than that of glutamate. Bromofuroate, an inhibitor of glutamate dehydrogenase, blocked oxidation of glutamate and of glutamine whereas aminoxyacetate, a transaminase inhibitor, had little or no effect with either substrate. These results indicate that glutamine metabolism is probably initiated by the conversion of glutamine to glutamate rather than to an alpha-keto acid. The localization of a glutaminase activity within avian liver mitochondria plus the absence of an active mitochondrial glutamine transaminase is consistent with the differential effects of the transaminase and glutamate dehydrogenase inhibitors. The high glutamine synthetase activity (40:1) suggests that mitochondrial catabolism of glutamine is minimal, freeing most of the glutamine synthesized for purine (uric acid) biosynthesis.
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PMID:Submitochondrial localization and function of enzymes of glutamine metabolism in avian liver. 1 18

Synthesis of glutamine synthetase (GS) in anaerobic batch cultures of Escherichia coli was repressed when excess NH4+ was available, but derepressed during growth with a poor nitrogen source. In wild-type bacteria there was only a weak inverse correlation between the activities of GS and glutamate dehydrogenase (GDH) during growth in various media. No positive correlations were found between the activities of GS and nitrite reductase, or between GS and cytochrome c552: both of these proteins were synthesized normally by mutants that contained no active GS. Although activities of GS and GDH were low in two mutants that are unable to synthesize cytochrome c552 or reduce nitrite because of defects in the nirA gene, the nirA defect was separated from the GS and GDH defects by transduction with bacteriophage P1. Attempts to show that catabolite repression of proline oxidase synthesis could be relieved during NH4+ starvation also failed. It is, therefore, unlikely that nitrite reduction or proline oxidation by E. coli are under positive control by GS protein. The regulation of the synthesis of enzymes for the utilization of secondary nitrogen sources in E. coli, therefore, different from that in Klebsiella aerogenes, but is similar to that in Salmonella typhimurium.
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PMID:Lack of a regulatory function for glutamine synthetase protein in the synthesis of glutamate dehydrogenase and nitrite reductase in Escherichia coli K12. 1 79

The product of a newly identified gene, glnF, which is distinct from the glutamine synthetase structural gene (glnA), is required for synthesis of glutamine synthetase [L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2[ in Salmonella typhimurium and probably in Escherichia coli. Salmonella strains with ICR (2-chloro-6-methoxy-9-[3-(2-chloroethyl)aminopropylamino]acridine dihyodrochloride)-induced (frameshift) mutations in glnF are glutamine auxotrophs; they have less than 10% oof wild-type glutamine synthetase activity or antigen and are unable to derepress the synthesis of the enzyme. The mutant allele is recessive to the wild-type allele, indicating that the glnF gene encodes a diffusible product. Mutant glnF strains have normal activities of all proteins involved in covalent modification of glutamine synthetase: adenylyltransferase (EC 2.7.7.42), PII, uridylyltransferase, and uridylyl removing enzyme. In addition, they have glutamate synthase (EC 1.4.1.13) and glutamate dehydrogenase (EC 1.4.1.4) activities. Thus, glnF does not encode the structure of any of these proteins. The above evidence suggests that the product of the glnF gene is (or produces) a positive regulatory factor that is required for synthesis of glutamine synthetase; it indicates that auto-regulation cannot account for control of the synthesis of glutamine synthetase in Salmonella.
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PMID:The product of a newly identified gene, gInF, is required for synthesis of glutamine synthetase in Salmonella. 1 62

Besides the synthesis of urea, ammonia detoxication at high concentrations can also be effected through enzyme reactions involved in glutamic acid metabolism. These mechanisms are also operative in extrahepatic tissues. Hyperammonemia is also found in the animal model of the portacaval shunt (PCS) rat. This model was chosen to study the activities of glutamate dehydrogenase, glutamine synthetase and glutaminase I in liver, brain and kidney 10, 20 and 30 days after PCS. In brain and kidney ammonia is detoxified mainly by the glutamate dehydrogenase and glutamine synthetase reactions whereas in the liver these enzyme reactions play a minor role.
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PMID:Enzymes of ammonia detoxication after portacaval shunt in the rat. II. Enzymes of glutamate metabolism. 2 34

A mutant (gltB) of Escherichia coli lacking glutamate synthase (GOGAT) was unable to utilize a wide variety of compounds as sole nitrogen source (e.g., arginine, proline, gamma-aminobutyrate, and glycine). Among revertants of these Asm- strains selected on one of these compounds (e.g., arginine, proline, or gamma-aminobutyrate) were those that produce glutamine synthetase (GS) constitutively (GlnC phenotype). These revertants had a pleiotropically restored ability to grow on compounds that are metabolized to glutamate. This suggested that the expression of the genes responsible for the metabolism of these nitrogen sources was regulated by GS. An examination of the regulation of proline oxidase confirmed this hypothesis. The differential sensitivities of GlnC and wild-type strains to low concentrations (0.1 mM) of the glutamine analog L-methionine-DL-sulfoximine supported the conclusion that the synthesis of a glutamine permease was also positively controlled by GS. During the course of this study we found that the reported position of the locus (gltB) for glutamate synthase is incorrect. We have relocated this gene to be 44% linked to the argG locus by P1 transduction. Further mapping has shown that the locus previously called aspB is in reality the gltB locus and that the "suppressor" of the aspB mutation (A. M. Reiner, J. Bacteriol. 97:1431-1436, 1969) is the locus for glutamate dehydrogenase (gdhA).
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PMID:gltB gene and regulation of nitrogen metabolism by glutamine synthetase in Escherichia coli. 2 35

The possible role of glutamate dehydrogenase, glutamate synthase, and glutamine synthetase in the regulation of enzyme formation in the gamma-aminobutyric acid (GABA) catabolic pathway of Escherichia coli K-12 was investigated. Evidence is presented indicating that glutamine synthetase acts as a positive regulator in the E. coli GABA control system. Mutations impairing glutamate synthase activity prevent the depression of the enzymes of the GABA pathway in ammonia-limited glucose media. However, mutations resulting in constitutive synthesis of glutamine synthetase (GlnC) restore the ability of the glutamate synthase-less mutants to grow in glucose-GABA media and result in depressed synthesis of the GABA enzymes. It is suggested that the loss of glutamate synthesis activity affects the GABA control system indirectly by lowering glutamine synthetase levels.
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PMID:Regulation of gamma-aminobutyric acid degradation in Escherichia coli by nitrogen metabolism enzymes. 2 37

The symbiotic, nitrogen-fixing bacterium Rhizobium sp. 32H1 is a specialized ammonium producer during symbiosis. However, during free-living growth, Rhizobium 32H1 assimilates ammonium very poorly. Two pathways of ammonium assimilation exist in enteric bacteria. One is mediated by glutamate dehydrogenase, and the other is mediated by glutamine synthetase-glutamate synthase. The former pathway is altogether inoperative in Rhizobium 32H1; the latter pathway operates at a slow rate and is under strict negative control by ammonium itself. Rhizobium 32H1 glutamine synthetase activity is modulated by both repression-derepression and reversible adenylylation. For a biochemical process lacking an alternative pathway, such a regulatory pattern exacerbates the very process. This suggests that Rhizobium 32H1 restricts its own ammonium assimilation to maximize the contribution of fixed nitrogen to the host plant during symbiosis.
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PMID:Control of ammonium assimilation in Rhizobium 32H1. 2 98

To determine whether Salmonella typhimurium has a nitrogen control response, we have examined the regulation of nitrogen utilization in two mutants with fivefold and threefold elevations in their glutamine synthetase activities. The mutants do not require glutamine for growth on glucose--ammonia medium but do have altered growth on other nitrogen sources. They grow better than an isogenic control on media containing arginine or asparate, but more slowly with proline or alanine as nitrogen sources. This unusual growth pattern is not due to altered regulation of the ammonia assimilatory enzymes, glutamate dehydrogenase and glutamate synthase, or to changes in the enzymes for aspartate degradation. However, transport for several amino acids may be affected. Measurement of amino acid uptake show that the mutants with high glutamine synthetase levels have increased rates for glutamine, arginine, aspartate, and lysine, but a decreased rate for proline. The relationship between glutamine synthetase levels and uptake was examined in two mutants with reduced, rather than increased, glutamine synthetase production. The uptake rates for glutamine and lysine were lower in these two glutamine auxotrophs than in the Gln+ controls. These results show a correlation between the glutamine synthetase levels and the uptake rates for several amino acids. In addition, the pleiotropic growth of the mutants with elevated glutamine synthetase activities suggests that a nitrogen control response exists for S. typhimurium and that it can be altered by mutations affecting glutamine synthetase regulation.
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PMID:Salmonella typhimurium LT-2 mutants with altered glutamine synthetase levels and amino acid uptake activities. 3 Jul 54

Rhodopseudomonas acidophila strain 7050 assimilated ammonia via a constitutive glutamine synthetase/glutamate synthase enzyme system. Glutamine synthetase had a Km for NH+4 of 0.38 mM whilst the nicotinamide adenine dinucleotide linked glutamate synthase had a Km for glutamine of 0.55 mM. R. acidophila utilized only a limited range of amino acids as sole nitrogen sources: L-alanine, glutamine and asparagine. The bacterium did not grow on glutamate as sole nitrogen source and lacked glutamate dehydrogenase. When R. acidophila was grown on L-alanine as the sole nitrogen source in the absence of N2 low levels of a nicotinamide adenine dinucleotide linked L-alanine dehydrogenase were produced. It is concluded, therefore, that this reaction was not a significant route of ammonia assimilation in this bacterium except when glutamine synthetase was inhibited by methionine sulphoximine. In L-alanine grown cells the presence of an active alanine-glyoxylate aminotransferase and, on occasions, low levels of an alanine-oxaloacetate aminotransferase were detected. Alanine-2-oxo-glutarate aminotransferase could not be demonstrated in this bacterium.
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PMID:Nitrogen assimilation in Rhodopseudomonas acidophila. 3 Nov 45

o-Aminobenzoic acid (OABA, anthranilic acid) and related compounds which are known to stimulate the biosynthesis of streptothricin-type antibiotic nourseothricin by Streptomyces noursei JA 3890b were found to increase strongly the NADH/NAD+ ratio in growing mycelium of this strain suggesting that these effectors are capable of interfering with the function of the respiratory chain. In parallel, a complex shift of metabolism was induced shown by simultaneous alteration of mycelial activities of alanine dehydrogenase, glutamine synthetase, and glutamate dehydrogenase. These changes may be responsible for the observed delay of amino acid catabolism and may improve the precursor supply of the secondary metabolism.
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PMID:Regulative influence of o-aminobenzoic acid on the biosynthesis of nourseothricin in cultures of Streptomyces noursei JA 3890b. III. Change of redox state of nicotinamide-adenine-dinucleotides in the presence of aminobenzoic acids. 3 66


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