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)

With either alanine or a mixture of 15 different amino acids as nitrogen source, the addition of L-leucine inhibited the synthesis of urea by isolated rat liver cells. With alanine present leucine promoted the production of glutamate and glutamine. Comparison of effects of leucine on soluble glutamate dehydrogenase, mitochondria and isolated cells supports the postulate that leucine exerts its effect through activation of glutamate dehydrogenase. It is suggested that this latter enzyme may not be as important for the production of NH3 for carbamoyl phosphate synthesis as has been considered hitherto.
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PMID:The effects L-leucine on the synthesis of urea, glutamate and glutamine by isolated rat liver cells. 80 18

Production of extracellular protease by Candida lipolytica NRRL Y-1094 was derepressed upon transfer to carbon-, nitrogen- or sulphur-free medium but not upon transfer to phosphorus-free medium. The protease activities produced under the three nutrient limitations had alkaline pH optima and similar substrate and inhibitor specificities. Any one of the following three conditions was found to be sufficient for derepression of extracellular protease: (a) "poor" carbon source, (b) cysteine intracellular pool below 0.5 micronmol/g dry weight cells and (c) ammonia intracellular pool below 10 micronmol/g dry weight cells. Thus, extracellular protease production in C. lipolytica was subject to at least three different regulatory controls, carbon, sulphur and nitrogen repression. Intracellular cysteine and ammonia appeared to be the metabolic signals for sulphur and nitrogen repression, respectively. Anabolic glutamate dehydrogenase did not act as a regulatory protein mediating nitrogen repression. Exogenous protein had an inductive effect on extracellular protease production.
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PMID:Regulation of extracellular protease production in Candida lipolytica. 87 75

Dicarboxylic amino acids constitute the most numerous residues of insoluble elastin in which are potentially ionizable in the physiological range of pH. These residues are essential in facilitating productive electrostatic interaction between elastase and elastin. The present study has investigated the possibility that the glutamic and aspartic acid residues of elastin are amidated. Acid-labile amide-bound ammonia of elastin was quantitated after hydrolysis of the insoluble protein with 2 M HC1 by incubating aliquots of microdistilled hydrolysates with glutamate dehydrogenase, excess alpha-ketoglutarate, and reduced nicotinamide adenine dinucleotide and measuring the resultant decrease in A340 due to oxidation of the dinucleotide cofactor. It was found that ligament elastin purified by repeated autoclaving contains approximately 2.29 mumol of acid-labile amide nitrogen per 10 mg of protein, a value equivalent to approximately 70% of the total number of dicarboxylic amino acid residues. Independent analysis of the amide content was obtained by amino acid analysis of an esterified and reduced elastin sample in which the free dicarboxylic amino acid residues had been converted to the corresponding alcohol derivatives. This analysis indicated that autoclaved ligament elastin contains approximately 18 glutamine, 3 asparagine, 4 glutamic acid and 5 aspartic acid residues per 1000 residues, in good agreement with the analysis of total acid-labile ammonia. The esterified and reduced elastin derivative was nearly inert as an elastase substrate, consistent with a lack of free dicarboxylic amino acid residues. However, addition of sodium dodecyl sulfate to this elastin derivative restores enzyme-substrate charge complementarity, and the elastin-ligand complex was readily hydrolyzed by elastase at the fully stimulated rate, emphasizing the control such ligands can exert in elastolysis. The amide bonds of elastin were found to be significantly more resistant to hydrolysis by 0.1 M NaOH at 98 degrees C than were those of lysozyme or free amidated amino acids. The finding that most of dicarboxylic amino acid residues of elastin exist at neutral amides further emphasizes the apolar character of elastin and has bearing upon the metabolic susceptibility, ligand-binding ability and structural aspects of this connective tissue protein.
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PMID:Amidated carboxyl groups in elastin. 93 66

Results of a histochemical study of glutamic dehydrogenase in experimental portal-systemic encephalopathy with hyperammonemia indicate that the enzyme's activity in brain was increased in all stages of the encephalopathy, and this increase appeared to be localized exclusively in astrocytes. The results are consistent with the view that the astrocyte has a critical role in ammonia metabolism in brain, probably in ammonia detoxification. The findings, moreover, indicate that one pool of glutamate, possibly the small pool, is located in the astrocyte.
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PMID:Histochemical studies in experimental portal-systemic encephalopathy. 94 32

Gyrocotyle fimbriata isolated from the spiral valve of Hydrolagus colliei were washed, then held in a filtered seawater-penicillin-Tris buffer medium. Ammonia and urea release to the medium declined together and ammonia production was minimal when the urea concentration was below detectable limits. Alanine and smaller amounts of glycine were released to the medium at a more constant rate. After 12 hr the alanine-glycine excretion was more than 20 times the ammonia excretion. L-arginine, L-serine, L-histidine, and urea were most effective in stimulating ammonia production by whole worms; other L-amino acids were essentially ineffective. L-glutamate dehydrogenase, L-amino acid oxidase, uricase, and ornithine transcarbamylase were below detectable levels. L-serine dehydrase, L-arginase, L-histidase, and urease were detected in tissue homogenates and probably account for most of the endogenous ammonia production. L-arginase has a molecular weight of 28,000 by Sehpadex gel filtration. The high levels of glutamate-pyruvate transaminase and lower levels of glutamate-oxalacetate transaminase correlate with the high level of alanine excretion. It is concluded that (1) ammonia production is not strongly linked to the overall energy metabolism of Gyrocotyle and is probably a result of a series of unrelated enzymatic reactions such as the action of urease of urea from the tissue of the rat fish, and (2) alanine and glycine are the major nitrogen excretory products and their production is linked to the energy metabolism of Gyrocotyle.
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PMID:Ammonia formation and amino acid excretion by Gyrocotyle fimbriata (Cestoidea). 111 78

The only exogenous substrates oxidized by mitochondria isolated from the flight muscle of the Japanese beetle (Popillia japonica) are proline, pyruvate and glycerol 3-phosphate. The highest rate of oxygen consumption is obtained with proline. The oxidation of proline leads to the production of more NH3 than alanine, indicating a functioning glutamate dehydrogenase (EC 1.4.1.2). Studies of mitochondrial extracts confirm the presence of a very active glutamate dehydrogenase, and this enzyme is found to be activated by ADP and inhibited by ATP. These extracts also show high alanine aminotransferase activity (EC 2.6.1.2) and a uniquely active "malic' enzyme (EC 1.1.1.39). The "malic' enzyme is activated by succinate and inhibited by ATP and by pyruvate. It is suggested that the input of tricarboxylate-cycle intermediate from proline oxidation is balanced by the formation of pyruvate from malate, and the complete oxidation of the majority of the pyruvate. Studies of the steady-state concentrations of mitochondrial CoASH and CoA thioesters during proline oxidation show a high succinyl (3-carboxypropionyl)-CoA content which falls on activating respiration with ADP. There is a concomitant rise in CoASH. However, the reverse transition, from state-3 to state-4 respiration, causes only very slight changes in acylation. The reasons for this are discussed. Studies of the mitochondrial content of glutamate, 2-oxoglutarate, malate, pyruvate, citrate and isocitrate during the same phases of proline oxidation give results consistent with control at the level of glutamate dehydrogenase and isocitrate dehydrogenase during proline oxidation, with the possibility of further control at "malic' enzyme. During the oxidation of pyruvate all of the tricarboxylate-cycle intermediates and NAD(P)H follow the pattern of changes described in the blowfly (Johnson & Hansford, 1975; Hansford, 1974) and isocitrate dehydrogenase is identified as the primary site of control.?2OAuthor
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PMID:The nature and control of the tricarboxylate cycle in beetle flight muscle. 120 Sep 85

Glutamate, glutamine, and ammonia pool size have been determined in two S. cerevisiae strains (GOGAT+ and GOGAT-) growing under ammonia excess and limitation at a dilution rate of 0.10/h. The biomass levels and glutamate dehydrogenase NADPH-dependent (NADPH-GDH) activities were also measured for both strains. The strain that lacks GOGAT activity showed lower levels of metabolites under both media and lower levels of biomass under carbon limitation (ammonia excess) compared to the GOGAT+ strain. Under nitrogen limitation, the biomass level was the same for both strains, but GOGAT- changed from rounded to ellipsoidal cells.
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PMID:Ammonia assimilation in S. cerevisiae under chemostatic growth. 132 53

We have studied the relative roles of the glutaminase versus glutamate dehydrogenase (GLDH) and purine nucleotide cycle (PNC) pathways in furnishing ammonia for urea synthesis. Isolated rat hepatocytes were incubated at pH 7.4 and 37 degrees C in Krebs buffer supplemented with 0.1 mM L-ornithine and 1 mM [2-15N]glutamine, [5-15N]glutamine, [15N]aspartate, or [15N]glutamate as the sole labeled nitrogen source in the presence and absence of 1 mM amino-oxyacetate (AOA). A separate series of incubations was carried out in a medium containing either 15N-labeled precursor together with an additional 19 unlabeled amino acids at concentrations similar to those of rat plasma. GC-MS was utilized to determine the precursor product relationship and the flux of 15N-labeled substrate toward 15NH3, the 6-amino group of adenine nucleotides ([6-15NH2]adenine), 15N-amino acids, and [15N]urea. Following 40 min incubation with [15N]aspartate the isotopic enrichment of singly and doubly labeled urea was 70 and 20 atom % excess, respectively; with [15N]glutamate these values were approximately 65 and approximately 30 atom % excess for singly and doubly labeled urea, respectively. In experiments with [15N]aspartate as a sole substrate 15NH3 enrichment exceeded that in [6-NH2]adenine, indicating that [6-15NH2]adenine could not be a major precursor to 15NH3. Addition of AOA inhibited the formation of [15N]glutamate, 15NH3 and doubly labeled urea from [15N]aspartate. However, AOA had little effect on [6-15NH2]adenine production. In experiments with [15N]glutamate, AOA inhibited the formation of [15N]aspartate and doubly labeled urea, whereas 15NH3 formation was increased. In the presence of a physiologic amino acid mixture, [15N]glutamate contributed less than 5% to urea-N. In contrast, the amide and the amino nitrogen of glutamine contributed approximately 65% of total urea-N regardless of the incubation medium. The current data indicate that when glutamate is a sole substrate the flux through GLDH is more prominent in furnishing NH3 for urea synthesis than the flux through the PNC. However, in experiments with medium containing a mixture of amino acids utilized by the rat liver in vivo, the fraction of NH3 derived via GLDH or PNC was negligible compared with the amount of ammonia derived via the glutaminase pathway. Therefore, the current data suggest that ammonia derived from 5-N of glutamine via glutaminase is the major source of nitrogen for hepatic urea-genesis.
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PMID:Relative role of the glutaminase, glutamate dehydrogenase, and AMP-deaminase pathways in hepatic ureagenesis: studies with 15N. 134 40

Response characteristics are presented for a dual-enzyme fiber-optic biosensor for glutamate. An enzyme layer composed of glutamate dehydrogenase (GDH) and glutamate-pyruvate transaminase (GPT) is used to produce reduced nicotinamide adenine dinucleotide (NADH) at the tip of a fiber-optic probe. NADH luminescence is monitored through this probe and the measured fluorescence intensity is related to the concentration of glutamate. GDH catalyzes the formation of NADH, and GPT drives the GDH reaction by removing a reaction product and regenerating glutamate. Optimal response is obtained in a pH 7.4 Tris-HCl buffer maintained at 25 degrees C in the presence of 4 mM NAD+ and 10 mM L-alanine. The temperature profile reveals a strong negative temperature effect which is attributed to the temperature dependency of NADH luminescence. Under optimal conditions, the sensor sensitivity is 0.127 nA/microM over the 1-10 microM concentration range, the detection limit is 0.13 microM, and response times range from 4 to 8 min. The sensor response is stable for 12 days when stored at 4 degrees C. Selectivity for glutamate is excellent over most of the common amino acids as well as ascorbic acid, uric acid, taurine, and GABA. Only slight responses were observed for glutamine and lysine. The effect of ammonia on the glutamate response was found to be minimal at total ammonia nitrogen concentrations as high as 200 microM.
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PMID:Dual-enzyme fiber-optic biosensor for glutamate based on reduced nicotinamide adenine dinucleotide luminescence. 135 Apr 33

The purification and some properties of NADP-dependent glutamate dehydrogenase (GDH) and glutamine synthetase (GS) from the facultatively anaerobic Gram-negative bacterium Paracoccus denitrificans were investigated. The enzymes were purified to homogeneity using a procedure which involved affinity chromatography on Blue Sepharose CL-6B as the major purification step. The recoveries in the purification of GDH and GS were 28% and 64%, respectively. The specific activity of purified GDH was 183 nkat (mg protein)-1 (deaminating reaction). GDH was composed of subunits of molecular mass 47 kDa and the native enzyme was either a tetramer or hexamer. The apparent Km values for L-glutamate, NADP, 2-oxoglutarate, NADPH and ammonia were 1.5 mM, 5.9 microM, 0.47 microM, 12.5 microM and 14 mM, respectively. The specific activity of purified GS was 1125 nkat (mg protein)-1 (transferase reaction). The molecular mass of native GS was 570 kDa; it was composed of 12 subunits of molecular mass 50.1 kDa. The apparent Km values for L-glutamine and hydroxylamine in the transferase reaction were 2.1 and 2.4 mM, respectively; those of ammonia, L-glutamate and ATP in the biosynthetic reaction were 0.03, 1 and 0.17 mM, respectively. After the adenylylation of GS, the Km for L-glutamine and L-glutamate increased and reached the values of 8.0 and 27 mM, respectively. The effects of the changes in GS activity on the ammonia metabolism of Paracoccus denitrificans are discussed.
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PMID:Purification and some properties of glutamate dehydrogenase and glutamine synthetase from Paracoccus denitrificans. 135 41


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