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 total of 41 mutants lacking NADP L-glutamate dehydrogenase (NADP-GDH) activity have been studied. All the mutations were located at the gdhA locus within 0-1% recombination of gdhAI. Two mutants, gdhAI and gdhA2, out of five examined, produced cross-reacting material which neutralized NADP-GDH anti-serum. The mutant gdhA9 has altered Km values for all five substrates: ammonium, alpha-ketoglutarate, l-glutamate, NADPH and NADP. The mutant gdhA20 had temperature-sensitive growth, abnormal ammonium-regulation characteristics and thermolabile NADP-GDH activity. These results show that gdhA is the structural gene for NADP-GDH.
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PMID:The structural gene for NADP L-glutamate dehydrogenase in Aspergillus nidulans. 23 11

When Escherichia coli was grown in a minimum medium with glucose as sole carbon source and a proper level of ammonia, NADP+ specific glutamate dehydrogenase (L-glutamate: NADP+ oxidoreductase (deaminating), ED 1.4.1.4) was induced. The enzyme was solubilized by French press treatment and purified to homogeneity by (NH4)2SO4 fractionation, heat treatment followed by DEAE-cellulose, hydroxylapatite and Bio-Gel chromatography with an overall yield of 30%. The enzyme proved to be heat stable and relatively resistant to protein denaturants. The optimum of enzymic activity for the reductive amination is at pH 8 and at pH 9 for the oxidative deamination. The activity is affected by adenine nucleotides. The molecular weight (about 250 000 for the native form and 46 000 for the inactive subunit) and amino acid composition, suggest strict similarities with the NADP+ enzyme from fungal origin.
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PMID:Glutamate dehydrogenase from Escherichia coli: induction, purification and properties of the enzyme. 23 98

Neurospora NADP-specific glutamate dehydrogenase that was treated with iodoacetate, iodoacetamide, or N-ethylmaleimide to block the thiol groups was cleaved with cyanogen bromide. Of the expected 10 peptides, based on a methionine content of 9 residues, 8 were obtained in pure form and 2 were handled as a mixture. The fragments ranged in size from 9 to 109 residues. In addition, there were isolated 6 peptides, produced by anomalous cleavage at the carboxyl groups of tryptophan residues, and two by hydrolysis of an aspartyl-proline bond. Preliminary separation of these peptides was accomplished by gel filtration followed by either ion-exchange chromatography of the larger peptides or by paper chromatography and paper electrophoresis of the smaller fragments. Ordering of the CNBr fragments in sequence was based upon sequences of tryptic and chymotryptic peptides obtained in another laboratory. The complete sequence of the protein is presented. The amino acid sequences of the bovine and chicken liver glutamate dehydrogenases previously determined show considerable homology with the NADP-specific enzyme of Neurospora in the NH2-terminal half of the molecule; this includes the region of the specifically reactive lysine residue and the portion of the sequence that has been implicated in coenzyme binding. Particularly striking is the fact that most of the residues conserved among the three homologous proteins would be expected to be important for conformational, rather than catalytic, effects. This implies that the conformation of the Neurospora enzyme must be similar in parts of its structure to the vertebrate enzymes but undoubtedly differs in some regards.
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PMID:Nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase of Neurospora. 23 97

The activities of the following enzymes were studied in connection with dinitrogen fixation in pea bacteroids: glutamine synthetase(L-glutamate: ammonia ligase (ADP-forming)(EC 6.3.1.2)(GS); glutamate dehydrogenase (NADP+)(L-glutamate: NADP+ oxidoreductase (deaminating)(EC 1.4.1.4)(GDH); glutamate synthase (L-glutamine: 2-exeglutarate aminotransferase (NADPH-oxidizing))(EC 2.6.1.53)(GOGAT). GS activity was high throughout the growth of the plant and GOGAT activity was always low. It is unlikely that GDH or the GS-GOGAT pathway can account for the incorporation of ammonia from dinitrogen fixation in the pea bacteroid,
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PMID:Enzymes of ammonia assimilation in Rhizobium leguminosarum bacteroids. 23 31

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

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

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 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

Malaria-infected red cells and free parasites have limited capabilities for the biosynthesis of amino acids. Therefore, the principal amino acid sources for parasite protein synthesis are the plasma free amino acids and host cell haemoglobin. Infected cells and plasmodia incorporate exogenously supplied amino acids into protein. However, the hypothesis that amino acid utilization (from an external source) is related to availability of that amino acid in haemoglobin is without universal support: it is true for isoleucine and for Plasmodium knowlesi and P. falciparum, but not for methionine, cysteine, and other amino acids, and it does not apply to P. lophurae. More by default than by direct evidence, haemoglobin is believed to be the main amino acid reservoir available to the intraerythrocytic plasmodium. Haemoglobin, ingested via the cytostome, is held in food vacuoles where auto-oxidation takes place. As a consequence, haem is released and accumulates in the vacuole as particulate haemozoin (= malaria pigment). Current evidence favours the view that haemozoin is mainly haematin. Acid and alkaline proteases (identified in crude extracts from mammalian and avian malarias) are presumably secreted directly into the food vacuole. They then digest the denatured globin and the resulting amino acids are incorporated into parasite protein. Cell-free protein synthesizing systems have been developed using P. knowlesi and P. lophurae ribosomes. In the main these systems are typically eukaryotic.Studies of amino acid metabolism are exceedingly limited. Arginine, lysine, methionine, and proline are incorporated into protein, whereas glutamic acid is metabolized via an NADP-specific glutamic dehydrogenase. Glutamate oxidation generates NADPH and auxiliary energy (in the form of alpha-ketoglutarate). The role of red cell glutathione in the economy of the parasite remains obscure. Important goals for future research should be: quantitative assessment of the relative importance of amino acid sources for parasite protein synthesis; purification and characterization of plasmodial proteinases; and in vitro translation of parasite messenger RNA.
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PMID:Amino acid metabolism and protein synthesis in malarial parasites. 33 83

Electrophoretic variation of the enzymes glucose phosphate isomerase, 6-phosphogluconate dehydrogenase, lactate dehydrogenase and glutamate dehydrogenase (NADP-dependent) has been studied in the African murine malaria parasites Plasmodium berghei, P. yoelii, P. vinckei and P. chabaudi and their subspecies. Horizontal starch gel electrophoresis was used throughout. The number of isolates examined in each subspecies varied from 1 (P. y. nigeriensis) to 24 (P. c. chabaudi). Extensive enzyme variation was found among isolates of most of the subspecies from which more than two such isolates were available for study. It is clear that the phenomenon of enzyme polymorphism is of common occurrence among malaria parasites. With the exception of P. berghei and P. yoelii, of which all isolates share an identical electrophoretic form of lactate dehydrogenase, no enzyme forms are shared between any of the 4 species of murine plasmodia. By contrast, within each species common enzyme forms are shared among each of the subspecies. The subspecies are nevertheless, distinguished from each other by the electrophoretic forms of at least one enzyme. The distribution and reassortment of enzyme variation among isolates of a single subspecies is in accordance with the concept of malaria parasites as sexually reproducing organisms. The study of variation among parasites present in individual wild-caught rodent hosts demonstrates that natural malarial infections usually comprise genetically heterogeneous populations of parasites. Nevertheless, the number of genetically distinct types of parasite of any one species present in a single infected host appears to be small. Generally not more than 2 or 3 clones of parasite of distinct genetic constitution are present in a single infected animal.
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PMID:Studies on enzyme variation in the murine malaria parasites Plasmodium berghei, P. yoelii, P. vinckei and P. chabaudi by starch gel electrophoresis. 35 25


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