Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.4.1.2 (glutamate dehydrogenase)
 4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Bacillus subtilis, the AhrC protein represses genes encoding enzymes of arginine biosynthesis and activates those mediating its catabolism. To determine how this repressor also functions as an activator, we attempted to clone catabolic genes by searching for insertions of the Tn917-lacZ transposon that express AhrC-dependent, arginine-inducible beta-galactosidase activity. One such isolate was obtained. The region upstream of lacZ was subcloned in Escherichia coli in such a way that it could be replaced in the B. subtilis chromosome after appropriate manipulation. Analysis of exonuclease III-derived deletions located an AhrC-dependent, arginine-inducible promoter to within a ca. 1.9 kb fragment. The sequence revealed: the 3' end of an ORF homologous to gdh genes encoding glutamate dehydrogenase, with highest homology to the homologue from Clostridium difficile; the 5' end of an ORF homologous to a Saccharomyces cerevisiae gene encoding delta 1-pyrroline 5-carboxylate dehydrogenase (P5CDH), an enzyme of arginine catabolism; and just upstream of the latter, a sequence with homology to known AhrC binding sites in the upstream part of the biosynthetic argCJBD-cpa-F cluster. The same region has also been sequenced by others as part of the B. subtilis genome sequencing project, revealing that the P5CDH gene is the first in a cluster termed rocABC. Restriction fragments containing the putative AhrC-binding sequence, but not those lacking it, showed retarded electrophoretic mobility in the presence of purified AhrC. A 277 bp AhrC-binding fragment also showed anomalous mobility in the absence of AhrC, consistent with its being intrinsically bent. DNAse I footprinting localized AhrC binding to bp -16/-22 to +1 (the transcription startpoint). Such a location for an activator binding site, i.e. overlapping the transcription start, is unusual.
Mol Gen Genet 1995 Aug 21
PMID:A binding site for activation by the Bacillus subtilis AhrC protein, a repressor/activator of arginine metabolism. 756 95

A soluble form of novel glutamate dehydrogenase has been purified from bovine brain. The preparation was homogeneous on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and composed of six identical subunits having a subunit size of 57,500 Da. The biochemical properties of glutamate dehydrogenase such as N-terminal amino acids sequences, kinetic parameters, amino acids analysis, and optimum pH were examined in both reductive amination of alpha-ketoglutarate and oxidative deamination of glutamate. N-terminal amino acid sequences of the bovine brain enzyme showed the significant differences in the first 5 amino acids compared to other glutamate dehydrogenases from various sources. These results indicate that glutamate dehydrogenase isolated from bovine brain is a novel polypeptide.
Biochem Mol Biol Int 1995 Aug
PMID:A novel glutamate dehydrogenase from bovine brain: purification and characterization. 758 Oct 4

The activity and some kinetic parameters of the key enzymes of the glycolysis, the gluconeogenesis and the amino acid catabolism from the liver of male and female mink have been determined and compared to the corresponding activities from rat and cat. The activities of glucose-6-phosphatase and pyruvate kinase are dependent on sex, both being higher in females. Except for pyruvate carboxylase the glycolytic and the gluconeogenic enzyme activities of the mink are higher than those of rat and cat; especially the activities of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase are markedly higher. The activities of glutamate dehydrogenase and glutamate oxaloacetate transaminase are smaller than the corresponding activities of rat but higher than those of cat. The results suggest that mink has a high capacity for gluconeogenesis compared to rat.
Comp Biochem Physiol B Biochem Mol Biol 1995 Sep
PMID:Activities of carbohydrate and amino acid metabolizing enzymes from liver of mink (Mustela vison) and preliminary observations on steady state kinetics of the enzymes. 758 47

The hexameric NAD-dependent glutamate dehydrogenase from the thermophilic eubacterium Bacillus acidocaldarius is the first glutamate dehydrogenase which spontaneously refolds in vitro. After 24 h unfolding in 6 M guanidinium chloride at 20 degrees C, refolding was achieved by dilution of the denaturant. The yield of reconstitution obtained in the presence of 1,4 dithio-DL-threitol in the unfolding/refolding mixture was 75%. The unfolding/refolding equilibria have been studied by fluorescence, circular dichroism and catalytic activity, which was 50% inhibited at 0.08 M guanidinium chloride, a value 30-fold lower than the transition midpoint detected by physical changes. Refolding was attempted in the presence of various additives, at different temperatures and varying enzyme and residual guanidinium chloride concentration. The refolded enzyme, after removal of inactive aggregated species, completely resembles the native enzyme in term of its physicochemical and kinetic properties as well as thermophilicity.
Biochem Mol Biol Int 1995 Feb
PMID:Refolding of glutamate dehydrogenase from Bacillus acidocaldarius after guanidinium chloride-induced unfolding. 766 95

This review is an exhaustive description of the biochemistry and enzymology of all 17 known NAD(P)(+)-amino acid dehydrogenases. These enzymes catalyze the oxidative deamination of an amino acid to its keto acid and ammonia, with the concomitant reduction of either NAD+ or NADP+. These enzymes have many important applications in industrial and medical settings and have been the object of prodigious enzymological research. This article describes all that is known about the poorly characterized members of the family and contains detailed information on the better characterized enzymes, including valine, phenylalanine, leucine, alanine, and glutamate dehydrogenases. The latter three enzymes have been the subject of extensive enzymological experimentation, and, consequently, their chemical mechanisms are discussed. The three-dimensional structure of the Clostridium symbiosum glutamate dehydrogenase has been determined recently and remains the only structure known of any amino acid dehydrogenase. The three-dimensional structure and its implications to the chemical mechanisms and rate-limiting steps of the amino acid dehydrogenase family are discussed.
Crit Rev Biochem Mol Biol 1994
PMID:The biochemistry and enzymology of amino acid dehydrogenases. 770 1

The gdhA gene of Synechocystis PCC 6803, which encodes an NADP-dependent glutamate dehydrogenase (NADP-GDH), has been cloned by complementation of an Escherichia coli glutamate auxotroph. This gene was found to code for a polypeptide of 428 amino acid residues, whose sequence shows high identity with those of archaebacteria (42-47%), some Gram-positive bacteria (40-44%) and mammals (37%). The minimal fragment of Synechocystis DNA required for complementation (2kb) carries the gdhA gene preceded by an open reading frame (ORF2) encoding a polypeptide of 130 amino acids. ORF2 and gdhA are co-transcribed as a 1.9 kb mRNA, but shorter transcripts including only gdhA were also detected. Two promoter regions were identified upon transcriptional fusion to the cat reporter gene of a promoter probe plasmid. Transcription from the promoter upstream of ORF2 was found to be regulated depending on the growth phase of Synechocystis, in parallel to NADP-GDH activity. This promoter is expressed in Escherichia coli too, in contrast to the second promoter, located between ORF2 and gdhA, which was silent in E. coli and did not respond to the stage of growth in Synechocystis. Disruption of the cyanobacterial gdhA gene with a chloramphenicol resistance cassette yielded a mutant strain totally lacking NADP-GDH activity, demonstrating that this gene is not essential to Synechocystis 6803 under our laboratory conditions.
Plant Mol Biol 1995 Apr
PMID:The NADP-glutamate dehydrogenase of the cyanobacterium Synechocystis 6803: cloning, transcriptional analysis and disruption of the gdhA gene. 778 82

The Leu3 protein of Saccharomyces cerevisiae has been shown to be a transcriptional regulator of genes encoding enzymes of the branched-chain amino acid biosynthetic pathways. Leu3 binds to upstream activating sequences (UASLEU) found in the promoters of LEU1, LEU2, LEU4, ILV2, and ILV5. In vivo and in vitro studies have shown that activation by Leu3 requires the presence of alpha-isopropylmalate. In at least one case (LEU2), Leu3 actually represses basal-level transcription when alpha-isopropylmalate is absent. Following identification of a UASLEU-homologous sequence in the promoter of GDH1, the gene encoding NADP(+)-dependent glutamate dehydrogenase, we demonstrate that Leu3 specifically interacts with this UASLEU element. We then show that Leu3 is required for full activation of the GDH1 gene. First, the expression of a GDH1-lacZ fusion gene is three- to sixfold lower in a strain lacking the LEU3 gene than in an isogenic LEU3+ strain. Expression is restored to near-normal levels when the leu3 deletion cells are transformed with a LEU3-bearing plasmid. Second, a significant decrease in GDH1-lacZ expression is also seen when the UASLEU of the GDH1-lacZ construct is made nonfunctional by mutation. Third, the steady-state level of GDH1 mRNA decreases about threefold in leu3 null cells. The decrease in GDH1 expression in leu3 null cells is reflected in a diminished specific activity of NADP(+)-dependent glutamate dehydrogenase. We also demonstrate that the level of GDH1-lacZ expression correlates with the cells' ability to generate alpha-isopropylmalate and is lowest in cells unable to produce alpha-isopropylmalate. We conclude that GDH1, which plays an important role in the assimilation of ammonia in yeast cells, is, in part, activated by a Leu3-alpha-isopropylmalate complex. This conclusion suggests that Leu3 participates in transcriptional regulation beyond the branched-chain amino acid biosynthetic pathways.
Mol Cell Biol 1995 Jan
PMID:The Saccharomyces cerevisiae Leu3 protein activates expression of GDH1, a key gene in nitrogen assimilation. 779 61

The mitochondrial FAD-linked enzyme glycerophosphate dehydrogenase plays a key role in the pancreatic B-cell glucose sensing device. In the present study, the activity of this enzyme was examined in islets of fa/fa rats in which inherited diabetes mellitus is associated with obesity, hyperinsulinism and severe insulin resistance. The specific activity of both FAD-linked glycerophosphate dehydrogenase and glutamate dehydrogenase were decreased in islet and liver homogenates prepared from fa/fa, as compared to Fa/Fa, rats, this coinciding with a low ratio between glutamateoxalacetate and glutamate-pyruvate transaminase activity in both islet and liver extracts, islet hyperplasia, hyperinsulinemia and hepatic steatosis in the hyperglycemic fa/fa rats. It is speculated that a low activity of FAD-linked glycerophosphate dehydrogenase in the pancreatic B-cell may participate to the perturbation of glucose homeostasis in fa/fa rats, like in other animal models of non-insulin-dependent diabetes mellitus.
Mol Cell Biochem 1994 Jun 29
PMID:Impaired FAD-glycerophosphate dehydrogenase activity in islet and liver homogenates of fa/fa rats. 783 41

This study aimed to compare the metabolic and secretory responses of pancreatic islets from animals with non-insulin-dependent diabetes to D-glucose with the effects of the methyl esters of succinic acid (SME) and glutamic acid (GME). The insulin secretory response to D-glucose was impaired in islets from rats with diabetes which was either inherited (Goto-Kakizaki (GK) rats) or acquired (streptozotocin-treated (STZ) rats). This coincided with a preferential alteration of oxidative relative to total glycolysis in intact islets and a selective defect of FAD-linked mitochondrial glycerophosphate dehydrogenase (m-GDH) in islet homogenates. This enzymatic defect was also found in purified B cells from STZ rats. It contrasted both with unaltered activities of glutamate dehydrogenase and succinate dehydrogenase in the islets of diabetic animals and with a normal or even increased activity of m-GDH in the livers of GK and STZ rats. The oxidation of [1,4-14C]SME and [U-14C]GME appeared decreased in islets of GK or STZ animals when compared with control rats, but no significant difference between control and diabetic rats was observed when the oxidative data were expressed relative to the rate of [U-14C]GME hydrolysis. Nevertheless, the absolute values for insulin release evoked by a non-metabolized analogue of L-leucine (BCH), by SME and by the association of BCH with either SME or GME were invariably lower in islets of GK and STZ rats than in those of control animals.(ABSTRACT TRUNCATED AT 250 WORDS)
J Mol Endocrinol 1994 Oct
PMID:Pancreatic islet response to dicarboxylic acid esters in rats with type 2 diabetes: enzymatic, metabolic and secretory aspects. 784 32

We have investigated the role of serotonergic neurons on the astrocytes catabolism of glutamate by analyzing glutamine synthetase (GS) and glutamate dehydrogenase (GDH) expression in the hippocampus after the degeneration of serotonergic neurons by a specific neurotoxin (5,7-DHT). 5,7-DHT caused reactive gliosis with hypertrophy (increase in glial fibrillary acidic protein (GFAP) expression) but not proliferation of astrocytes. Glutamate metabolism appeared preferentially regulated by a control of GDH expression rather than GS since the expression of GDH was specifically and significantly induced in the hippocampus whereas the level of GS remained unchanged. The inhibition of serotonin synthesis (by para-chlorophenylalanine (p-CPA) administration) produced no significant increase of GDH level. This suggests that serotonin is not the principal factor involved in this control of GDH expression.
Brain Res Mol Brain Res 1994 Oct
PMID:Modifications of glial metabolism of glutamate after serotonergic neuron degeneration in the hippocampus of the rat. 785 35


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