Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.4.1.4 (glutamate dehydrogenase)
 4,358 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A variety of metabolites have been found to elicit a form of inhibition or activation on an NAD-specific glutamate dehydrogenase (NAD-GDH, EC 1.4.1.2) from Halobacterium halobium. The purified halophilic enzyme was tested with several compounds known to be allosteric modifiers of mammalian glutamate dehydrogenases to determine their effects on enzyme activity. GTP, ATP, ADP and AMP did not affect the enzyme, so these effectors of bovine glutamate dehydrogenase do not play a role in the regulation of the halophilic enzyme. However, the halophilic enzyme was subject to strong inhibition by TCA intermediates. When measuring the initial rate of the reaction, the oxidative deamination of L-glutamate was inhibited by TCA metabolites such as: fumarate, oxalacetate, succinate and malate; by substrate analogues such as: NADP+, D-glutamate and glutarate; and by dicarboxylic compounds such as adipate. On the other hand, all the amino acids tested were activators of this enzyme, except the D-isomer of the substrate L-glutamate that acted as an inhibitor. The relative effectiveness of each inhibitor or activator (Ki or Ka values) was correlated with the dipole moment (mu), HOMO and LUMO molecular orbital energies, optimal distance between two carboxyl groups, and hydrophobicity. Compounds with high dipole moment acted as good activators while compounds with low dipole moment were inhibitors. We have also found that the best activators were amino acids with no polar lateral chain.
 ...
PMID:NAD-glutamate dehydrogenase from Halobacterium halobium: inhibition and activation by TCA intermediates and amino acids. 860 24

In Saccharomyces cerevisiae, carbon and nitrogen metabolisms are connected via the incorporation of ammonia into glutamate; this reaction is catalyzed by the NADP-dependent glutamate dehydrogenase (NADP-GDH) encoded by the GDH1 gene. In this report, we show that the GDH1 gene requires the CCAAT box-binding activator (HAP complex) for optimal expression. This conclusion is based on several lines of evidence: (1) overexpression of GDH1 can correct the growth defect of hap2 and hap3 mutants on ammonium sulfate as a nitrogen source, (ii) Northern (RNA) blot analysis shows that the steady-state level of GDH1 mRNA is strongly lowered in a hap2 mutant, (iii) expression of a GDH1-lacZ fusion is drastically reduced in hap mutants, (iv) NADP-GDH activity is several times lower in the hap mutants compared with that in the isogenic wild-type strain, and finally, (v) site-directed mutagenesis of two consensual HAP binding sites in the GDH1 promoter strongly reduces expression of GDH1 and makes it HAP independent. Expression of GDH1 is also regulated by the carbon source, i.e., expression is higher on lactate than on ethanol, glycerol, or galactose, with the lowest expression being found on glucose. Finally, we show that a hap2 mutation does not affect expression of other genes involved in nitrogen metabolism (GDH2, GLN1, and GLN3 encoding, respectively, the NAD-GDH, glutamine synthetase, and a general activator of several nitrogen catabolic genes). The HAP complex is known to regulate expression of several genes involved in carbon metabolism; its role in the control of GDH1 gene expression, therefore, provides evidence for a cross-pathway regulation between carbon and nitrogen metabolisms.
 ...
PMID:The CCAAT box-binding factor stimulates ammonium assimilation in Saccharomyces cerevisiae, defining a new cross-pathway regulation between nitrogen and carbon metabolisms. 860 56

Two forms of the NAD-dependent glutamate dehydrogenase were partially purified from Dictyostelium discoideum, an activated and a non-activated form. V(max) for the non-activated enzyme was stimulated 88-fold and the activated enzyme 3-fold by 0.1 mM AMP (at their pH optima). Half maximal stimulation by AMP is achieved at 221 +/- 39 microM for the non-activated enzyme and 20 +/- 2 microM for the activated enzyme. We have shown that activation of NAD-GDH in vivo has many similarities to trypsin treatment of non-activated enzyme and that proteolysis is the probable mechanism of activation.
 ...
PMID:Kinetic properties and the mechanism of activation of NAD-dependent glutamate dehydrogenase from Dictyostelium discoideum. 872 2

An osmosensitive mutant of Escherichia coli was isolated and shown to harbor two mutations that were together necessary for osmosensitivity. One (ossB) was an insertion mutation in the gltBD operon, which encodes the enzyme glutamate synthase (GOGAT), involved in ammonia assimilation and L-glutamate biosynthesis. The other (ossA) was in the fnr gene, encoding the regulator protein FNR for anaerobic gene expression. Several missense or deletion mutations in fnr and gltBD behaved like ossA and ossB, respectively, in conferring osmosensitivity. A mutation affecting the DNA-binding domain of FNR was recessive to fnr+ with respect to the osmotolerance phenotype but was dominant-negative for its effect on expression of genes in anaerobic respiration. Our results may most simply be interpreted as suggesting the requirement for monomeric FNR during aerobic growth of E. coli in high-osmolarity media, presumably for L-glutamate accumulation via the GOGAT-independent pathway (catalyzed by glutamate dehydrogenase [GDH]), but the mechanism of FNR action is not known. We also found that the spoT gene (encoding guanosine 3',5'-bispyrophosphate [ppGpp] synthetase II/ppGpp-3' pyrophosphohydrolase), in multiple copies, overcomes the defect in NH4+ assimilation associated with GOGAT deficiency and thereby suppresses osmosensitivity in gltBD fnr strains. Enhancement of GDH activity in these derivatives appears to be responsible for the observed suppression. Its likely physiological relevance was established by the demonstration that growth of gltBD mutants (that are haploid for spoT+) on moderately low [NH4+] was restored with the use of C sources poorer than glucose in the medium. Our results raise the possibility that SpoT-mediated accumulation of ppGpp during C-limited growth leads to GDH activation and that the latter enzyme plays an important role in N assimilation in situ hitherto unrecognized from studies on laboratory-grown cultures.
 ...
PMID:Roles of SpoT and FNR in NH4+ assimilation and osmoregulation in GOGAT (glutamate synthase)-deficient mutants of Escherichia coli. 876 38

The activities of FAD-linked glycerophosphate dehydrogenase (m-GDH), glutamate dehydrogenase (GlDH), glutamate-pyruvate transaminase (GPT) and glutamate-oxalacetate transaminase (GOT) were measured in purified populations of CD3+ lymphocytes from 55 control subjects, 62 type-2 diabetics and 50 non-diabetic relatives of the latter patients. The activity of m-GDH was measured by both a radioisotopic procedure and colourimetric technique. As judged from these measurements and relative to the paired value for GlDH, the incidence of abnormally low m-GDH activity was significantly higher in type-2 diabetics than in control subjects. Moreover, the paired ratio in reaction velocity between the colourimetric and radioisotopic assay of m-GDH was abnormally high in patients with low m-GDH activity. Low m-GDH activity often coincided with increased GPT activity in plasma or high GPT/GOT ratio in lymphocytes. No obvious clustering of these anomalies was found in relatives of diabetic patients. These findings suggest that an inherited or acquired genomic defect of m-GDH in lymphocytes, and possibly in pancreatic B-cells, may participate to the pathogenesis of non-insulin-dependent diabetes mellitus.
 ...
PMID:FAD-glycerophosphate dehydrogenase activity in lymphocytes of type-2 diabetic patients and their relatives. 879 98

The activities of the mitochondrial FAD-linked glycerophosphate dehydrogenase (m-GDH), glutamate dehydrogenase, alpha-ketoglutarate dehydrogenase, glutamate-pyruvate transaminase (GPT) and glutamate-oxaloacetate transaminase were measured in islet and liver homogenates from fetal, neonatal, adult male, adult female, pregnant and lactating rats. Either parallel or dissociated ontogenic changes were observed in islet and liver homogenates. The activity of islet m-GDH was slightly, albeit not significantly, lower in neonates than in adult rats, comparable in male and female adult animals, unaffected by pregnancy, and increased during lactation. It was much higher in fetal or adult islets cultured for 7 days than in freshly isolated islets from adult rats. In cultured islets from adult rats, the increase in m-GDH activity coincided with a dramatic decrease of GPT activity, a situation the mirror image of that found in several animal models of non-insulin-dependent diabetes mellitus. The intrinsic properties of m-GDH, as judged by comparison of measurements made by either a radioisotopic or a colorimetric procedure, were not identical in islet and liver homogenates and differed between fetal and adult islets, suggesting the existence of distinct iso-enzymes. These findings illustrate adaptive changes of islet enzymes, with exclusive or partial mitochondrial location, in ontogenic situations characterized by a remodelling of fuel homeostasis.
 ...
PMID:Ontogeny of FAD-linked glycerophosphate dehydrogenase in rat pancreatic islets. 879 9

We studied the level(s) at which glutamate dehydrogenase (GDH; EC 1.4.1.2) expression is regulated in the livers of fed male and female rats. The cellular content of GDH mRNA, protein, and enzyme activity was determined quantitatively using image analysis for measurement of the absorbance in consecutive serial sections that were processed for in situ hybridization, immunohistochemistry, and enzyme histochemistry. In both males and females, GDH protein and activity patterns were similar, with pericentral values being twice as high as periportal values. GDH mRNA distribution patterns in female liver lobules reflected those of GDH protein and activity, but GDH mRNA distribution patterns in male rat livers were found to be homogeneous owing to a more than twofold lower cellular mRNA content in pericentral zones than in female rats. We conclude that gender affects GDH expression selectively in pericentral zones at posttranscriptional and pretranslational levels.
 ...
PMID:Gender-dependent regulation of glutamate dehydrogenase expression in periportal and pericentral zones of rat liver lobules. 881 80

Nicotinamide adenine dinucleotide-specific glutamate dehydrogenase (NAD-GDH; EC 1.4.1.3) from Amphibacillus xylanus DSM 6626 was enriched 100-fold to homogeneity. The molecular mass was determined by native polyacrylamide electrophoresis and by gel filtration to be 260 kDa (+/- 25 kDa); the enzyme was composed of identical subunits of 45 (+/- 5) kDa, indicating that the native enzyme has a hexameric structure. NAD-GDH was highly specific for the coenzyme NAD(H) and catalyzed both the formation and the oxidation of glutamate. Apparent Km-values of 56 mM glutamate, 0.35 mM NAD (oxidative deamination) and 6.7 mM 2-oxoglutaric acid, 42 mM NH4Cl and 0.036 mM NADH (reductive amination) were measured. The enzyme was unusually resistant towards variation of pH, chaotropic agents, organic solvents, and was stable at elevated temperature, retaining 50% activity after 120 min incubation at 85 degrees C.
 ...
PMID:Unusually stable NAD-specific glutamate dehydrogenase from the alkaliphile Amphibacillus xylanus. 883 45

Malaysian, African and Thai Plasmodium falciparum isolates were cultured in vitro by the Trager and Jensen method (1976; 1977) and were later cloned by the limiting dilution method (Rosario, 1981). Forty-eight clones were obtained and were characterized by electrophoretic variations of GDH (NADP-dependent glutamate dehydrogenase)(EC. 1.4.1.4). It was found that they were pure clones because they possessed either GDH-1 or GDH-2 unlike their parent isolates which exhibited both GDH-1 and GDH-2.
 ...
PMID:Electrophoretic variations of enzyme, GDH (NADP-dependent glutamate dehydrogenase)(EC. 1.4.1.4) in characterizing clones and isolates of Malaysian Plasmodium falciparum. 884 98

Photoaffinity labeling with [gamma-32P]8N3GTP (8-azidoguanosine triphosphate) was used to identify the guanine binding peptides of the GTT binding site within two types of glutamate dehydrogenase isoproteins (GDH I and GDH II) isolated from bovine brain. 8N3GTP, without photolysis, mimicked the inhibitory properties of GTP on GDH I and GDH II activities. Saturation of photoinsertion of GDH isoproteins revealed an apparent Kd of 8 microM (GDH I) and 24 microM (GDH II) for [gamma-32P]8N3GTP. Ion exchange and reversed-phase high-performance liquid chromatography (HPLC) were used to isolate photolabel-containing peptides generated with trypsin. This identified a portion of the guanine binding domain within the GTP binding site is the region containing the sequence I-S-G-A-S-E-X-D-I-V-H-S-A-L-A-Y-T-M E-R (GDH I) and I-S-G-A-S-E-X-D-I-V-H-S-G-L-A-Y-T-M-E-R (GDH II). The symbol X indicates a position for which no phenylthiohydantoin-amino acid could be assigned. The missing residue, however, can be designated as a photolabeled lysine since the sequences including the lysine residue in question have a complete identity with those of the other GDH species known. Also, trypsin was unable to cleave the photolabeled peptide at this site. Photolabeling of these peptides was prevented by the presence of GTP during photolysis, while other nucleotides could not reduce the amount of photoinsertion as effectively as GTP. These results demonstrate selectivity of the photoprobe for the GTP binding site and suggest that the peptide identified using the photoprobe is located in the GTP binding domain of the brain GDH isoproteins.
 ...
PMID:Identification of a peptide of the guanosine triphosphate binding site within brain glutamate dehydrogenase isoproteins using 8-azidoguanosine triphosphate. 890 87


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>