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:1.4.1.4 (glutamate dehydrogenase)
4,358 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Stopped flow studies of D2O kinetic solvent isotope effects on the reaction catalyzed by L-glutamate dehydrogenase reveal, in addition to several effects apparently attributable simply to pKa shifts, a 2-fold pH-independent effect on the velocity of the steady state oxidative deamination of L-glutamate by enzyme and NADP. Comparable pH-independent D2O kinetic solvent isotope effects are seen both in a transient phase of the reaction in which alpha-ketoglutarate is displaced by L-glutamate from an enzyme-NADPH-alpha-ketoglutarate (product) complex and in an analogous model reaction in which alpha-ketoglutarate is displaced by D-glutamate. These results suggest that alpha-ketoglutarate dissociation from an enzyme-NADPH-alpha-ketoglutarate complex is rate-limiting in the steady state.
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PMID:Location of deuterium oxide solvent isotope effects in the glutamate dehydrogenase reaction. 23 82

The levels of glutamate synthase and of glutamine synthetase are both derepressed 10-fold in strain JP1449 of Escherichia coli carrying a thermosensitive mutation in the glutamyl-transfer ribonucleic acid (tRNA) synthetase and growing exponentially but at a reduced rate at a partially restrictive temperature, compared with the levels in strain AB347 isogenic with strain JP1449 except for this thermosensitive mutation and the marker aro. These two enzymes catalyze one of the two pathways for glutamate biosynthesis in E. coli, the other being defined by the glutamate dehydrogenase. We observed a correlation between the percentage of charged tRNAGlu and the level of glutamate synthase in various mutants reported to have an altered glutamyl-tRNA synthetase activity. These results suggest that a glutamyl-tRNA might be involved in the repression of the biosynthesis of the glutamate synthase and of the glutamine synthetase and would couple the regulation of the biosynthesis of these two enzymes, which can work in tandem to synthesize glutamate when the ammonia concentration is low in E. coli but whose structural genes are quite distant from each other. No derepression of the level of the glutamate dehydrogenase was observed in mutant strain JP1449 under the conditions where the levels of the glutamine synthetase and of the glutamate synthase were derepressed. This result indicates that the two pathways for glutamate biosynthesis in E. coli are under different regulatory controls. The glutamate has been reported to be probably the key regulatory element of the biosynthesis of the glutamate dehydrogenase. Our results indicate that the cell has chosen the level of glutamyl-tRNA as a more sensitive probe to regulate the biosynthesis of the enzymes of the other pathway, which must be energized at a low ammonia concentration.
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PMID:Derepressed levels of glutamate synthase and glutamine synthetase in Escherichia coli mutants altered in glutamyl-transfer ribonucleic acid synthetase. 23 24

Neurospora glutamate dehydrogenase (NADP-specific) is rapidly inactivated upon reaction with tetranitromethane. This inactivation is completely prevented by the presence of coenzyme (NADP) or nicotinamide mononucleotide (NMN) but not by substrate. NADH, or 2'-monophosphoadenosine-5'-diphosphoribose. Amino acid analysis indicates that the primary effect of modification is nitration of a single residue of tyrosine per polypeptide chain. We have identified the reactive tyrosine by isolation of a single, uniquely labeled peptide after hydrolysis with trypsin followed by cleavage with cyanogen bromide. The modified residue proved to be tyrosine-168 in the linear sequence. This residue is not present in the part of the sequence that had been previously implicated as involved in the binding of the adenylate portion of the coenzyme. Both NMN and 2-monophosphoadenosine-5'-diphosphoribose act as competitive inhibitors of NADP in the oxidation of glutamate with Ki values of 4.65 x 10(-4) M and 4.30 x 10(-4) M, respectively. Thus, the specific protection afforded by NADP and NMN, but not by 2'-monophosphoadenosine-5'-diphosphoribose, indicates that tyrosine-168 is involved in binding the nicotinamide portion of the coenzyme.
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PMID:Nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase of Neurospora. III. Inactivation by nitration of a tyrosine residue involved in coenzyme binding. 23 46

The theoretical and experimental analysis of a reversible association-dissociation equilibrium between different proteins (mixed association) is described. The experiments were performed with glutamate dehydrogenases from beef and rat liver. These enzymes are different, especially with respect to their association behavior. The association constant of rat liver glutamate dehydrogenase has been determined by light-scattering measurements. Its value (1.3 x 10(-4) M(-1)) is much lower than that of the beef liver enzyme, but the difference in the free association energy is only 30%. Association between these two enzymes is observed, also employing light-scattering experiments. Theoretical curves for mixed associating systems have been calculated and by comparison with these curves the mixed association constant could be determined. Since the free association energy of the mixed association is very near to the arithmetic mean between the values for the pure enzymes, the association interactions appear to be additive. The model of an open association with a virial coefficient is also true for the rat enzyme and the mixed association. The ultracentrifuge data are also explained by the same model and yield a similar value for the mixed association constant. Differences in the enzyme kinetics are small, but a somewhat reduced lifetime of the ternary complexes with the coenzymes and with subs-rates or GTP can be concluded for the rat liver enzyme. The circular dichroism measurements indicate no significant difference in the dissociation constants of the nucleotides, but the different amplitudes of the ellipticity indicate small differences in the electrical environment of the active center.
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PMID:Quantitative analysis of mixed association between different protein molecules. Physico-chemical and enzymatic properties of rat-liver glutamate dehydrogenase. 24 Jun 77

Optical characteristics of enzyme-reduced coenzyme complexes of yeast NADP-specific glutamate dehydrogenase have been investigated in the presence and absence of product (L-glutamate) and in the presence or absence of phosphate. The phosphate effect, pointed out in a previous work, is found again: inorganic phosphate (Pi) destabilizes the binary complex (E - NADPH), the dissociation constant of which is equal to 14 muM, a value much higher than that determined in Tris-HCl buffer: Kd = 0.9 muM. Concerning the role of phosphate some assumptions are drawn up with respect to a similar behaviour of Pi toward yeast glutamate dehydrogenase and ADP toward the beef liver enzyme. In the same way, L-glutamate induces a stabilization of the binary complex; this latter effect is unchanged in the presence of phosphate, yet it is less marked than in the case of beef liver glutamate dehydrogenase. Protein fluorescence, nucleotide fluorescence and circular dichroism measurements allowed the determination of three identical and independent NADPH binding sites per hexameric active unit. In analogy with beef liver enzyme, it seems that yeast glutamate dehydrogenase is a good model to study anticooperativity in ligand binding.
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PMID:Binding studies of NADPH to NADP-specific L-glutamate dehydrogenase from Saccharomyces cerevisiae. 24 Jul 22

The effect of boseimycin on the in vitro activity and in vivo synthesis of alkaline phosphatase, aconitase and lactate, isocitrate, glutamate and alanine dehydrogenases was studied in Bacillus subtilis. At a subinhibitory concentration, synthesis of glutamate dehydrogenase was stimulated but alkaline phosphatase, lactate dehydrogenase and aconitase synthesis was inhibited. On the contrary, boseimycin inhibited slightly the activity of lactate dehydrogenase in cell-free extracts. Glutamate dehydrogenase and aconitase activities were not affected.
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PMID:Effect of boseimycin on some enzyme systems of Bacillus subtilis. 24 Jul 61

The regulation of glutamate dehydrogenase (EC 1.4.1.4), glutamine synthetase (EC 6.3.1.2), and glutamate synthase (EC 2.6.1.53) was examined for cultures of Salmonella typhimurium grown with various nitrogen and amino acid sources. In contrast to the regulatory pattern observed in Klebsiella aerogenes, the glutamate dehydrogenase levels of S. typhimurium do not decrease when glutamine synthetase is derepressed during growth with limiting ammonia. Thus, it appears that the S. typhimurium glutamine synthetase does not regulate the synthesis of glutamate dehydrogenase as reported for K. aerogenes. The glutamate dehydrogenase activity does increase, however, during growth of a glutamate auxotroph with glutamate as a limiting amino acid source. The regulation of glutamate synthase levels is complex with the enzyme activity decreasing during growth with glutamate as a nitrogen source, and during growth of auxotrophs with either glutamine or glutamate as limiting amino acids.
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PMID:Regulation of the ammonia assimilatory enzymes in Salmonella typhimurium. 24 Aug 4

The rate of transport of L-amino acids by Saccharomyces cerevisiae epsilon 1278b increased with time in response to nitrogen starvation. This increase could be prevented by the addition of ammonium sulfate or cycloheximide. A slow time-dependent loss of transport activity was observed when ammonium sulfate (or ammonium sulfate plus cycloheximide) was added to cells after 3 h of nitrogen starvation. This loss of activity was not observed in the presence of cycloheximide alone. In a mutant yeast strain which lacks the nicotinamide adenine dinucleotide phosphate-dependent (anabolic) glutamate dehydrogenase, no significant decrease in amino acid transport was observed when ammonium sulfate was added to nitrogen-starved cells. A double mutant, which lacks the nicotinamide adenine dinucleotide phosphate-dependent enzyme and in addition has a depressed level of the nicotinamide adenine dinucleotide-dependent (catabolic) glutamate dehydrogenase, shows the same sensitivity to ammonium ion as the wild-type strain. These data suggest that the inhibition of amino acid transport by ammonium ion results from the uptake of this metabolite into the cell and its subsequent incorporation into the alpha-amino groups of glutamate and other amino acids.
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PMID:Inhibition of amino acid transport by ammonium ion in Saccharomyces cerevisiae. 24 Aug 6

Two strains of Cyanidium caldarium, one able to utilize nitrate as a substrate, and the other not, were tested for the presence of enzymes of ammonia assimilation. The nitrate-assimilating strain exhibits glutamate dehydrogenase activity. By contrast, the other strain lacks glutamate dehydrogenase; it possesses high alanine dehydrogenase and L-alanine aminotransferase activities which suggest that this strain may incorporate ammonia through reductive amination of pyruvate and may form glutamate from 2-ketoglutarate by a transamination reaction with alanine. Neither strain reveals glutamate synthase activity. Both strains contain similar levels of glutamine synthetase.
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PMID:Observations on enzymes of ammonia assimilation in two different strains of Cyanidium caldarium. 24 91

The effects of 0-30% methanol (vol/vol) on the Km an Vm values for both the forward and reverse directions of the L-glutamate dehydrogenase reaction were determined at 0 degrees C. The decrease in temperature alone had very little effect on these parameters. However, in the forward reaction, 30% methanol resulted in a 14-fold decrease in the Km value for glutamate, a slight decrease in the Km value for NADP, and a thirty-fold decrease in Vm. Substrate inhibition by glutamate was observed at concentrations greater than 4 mM. In the reverse reaction, 30% methanol caused a decrease in the Km values for alpha-ketoglutarate and ammonia and a 10-fold decrease in Vm. Substrate inhibition by both alpha-ketoglutarate and NADPH was observed at concentrations of either substrate above 0.03 mM. The dependence of Km for glutamate and Vm values for the forward reaction on methanol concentration suggests that they are similarly affected by methanol, in direct contrast to results obtained for NADP. Methanol appeared to cause a general tightening of complexes, which may arise from an effect on the "activities" of species in solution. The use of methanol not only allows for the study of reaction intermediates by slowing the reaction with the cryogenic method, but may also serve as a mechanistic probe by affecting several polarity as well as Km, Vm, and K1 values.
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PMID:The effects of methanol on the glutamate dehydrogenase reaction at 0 degrees C. 26 5


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