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

---

Query: EC:1.4.3.11 (glutamate dehydrogenase)
4,437 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pathways of glutamine metabolism in resting and proliferating rat thymocytes and established human T- and B-lymphoblastoid cell lines were evaluated by in vitro incubations of freshly prepared or cultured cells for one to two hours with [U14C]glutamine. Complete recovery of glutamine carbons utilized in products allowed quantification of the pathways of glutamine metabolism under the experimental conditions. Partial oxidation of glutamine via 2-oxoglutarate in a truncated citric acid cycle to CO2 and oxaloacetate, which then was converted to aspartate, accounted for 76% and 69%, respectively, of the glutamine metabolized beyond the stage of glutamate by resting and proliferating thymocytes. Similar results were obtained with the lymphoblastoid T- and B-cell lines. Complete oxidation to CO2 in the citric acid cycle via 2-oxoglutarate dehydrogenase and isocitrate dehydrogenase accounted for only 25% and 7%, respectively. In proliferating cells a substantial amount of glutamine carbons was also recovered in pyruvate, alanine, and especially lactate. The main route of glutamine and glutamate entrance into the citric acid cycle via 2-oxoglutarate in lymphocytes appears to be transamination by aspartate aminotransferase rather than oxidative deamination by glutamate dehydrogenase. In the presence of glucose as a second substrate, glutamine utilization and aspartate formation markedly decreased, but complete oxidation of glutamine carbons to CO2 increased to 37% and 23%, respectively, in resting and proliferating cells. The dipeptide, glycyl-L-glutamine, which is more stable than free glutamine, can substitute for glutamine in thymocyte cultures at higher concentrations.
...
PMID:Metabolism of glutamine in lymphocytes. 256 63

LLC-PK1 kidney epithelial cells grown under the condition of continuous rocking exhibit a variety of differentiated functions of proximal tubular epithelium, including pH-modulated ammoniagenesis. To further determine their value as a model system, we investigated the pathways of ammoniagenesis under both normal conditions and acid-base manipulations. Pulse-chase studies with carbon 14-labeled glutamine demonstrated a marked delay in glutamine conversion to glutamate, indicating that glutamine deamidation is a critical rate-limiting step, and also provided evidence for metabolism of the glutamine carbon skeleton by the tricarboxylic acid cycle. Ammonia and alanine were the predominant nitrogen metabolites of glutamine at all pH conditions, and the stoichiometry suggested that glutamate is metabolized through both glutamate dehydrogenase and glutamate transaminase at pH 7.4. Increased ammonia production in response to a low pH was associated with increased flux through phosphate-dependent glutaminase and the glutamate transamination pathway and was accompanied by a fall in intracellular glutamate and alpha-ketoglutarate concentrations, which was similar to events in the intact kidney. Studies with the inhibitors acivicin and amino oxyacetate suggested that the gamma-glutamyltranspeptidase and glutamine transamination pathways are inconsequential in LLC-PK1 cells. The phosphate-dependent glutaminase pathway appears to play a predominant role in the regulation of ammoniagenesis. The similarity in ammonia metabolism with other in vitro and in vivo models suggests that LLC-PK1 cells will be a useful system for investigating renal ammoniagenesis and the intracellular signals that modulate this process.
...
PMID:Pathways and regulation of ammoniagenesis by the LLC-PK1 cells in culture. 257 Jan 15

The effects of sodium valproate, a widely used antiepileptic drug and an hyperammonemic agent, on glutamine and glutamate metabolism were studied in isolated dog kidney tubules. Valproate markedly stimulated glutamine removal as well as the formation of ammonia, aspartate, pyruvate, lactate, alanine and glucose; the increase in ammonia formation was explained by a stimulation by valproate of flux not only through glutaminase (EC 3.5.1.2) but also through glutamate dehydrogenase (EC 1.4.1.3). By contrast, valproate did not stimulate glutamate removal or ammonia, aspartate and glucose formation from glutamate; this suggests that the increase in flux through glutamate dehydrogenase with glutamine as substrate was secondary to the increase in flux through glutaminase. Accumulation of pyruvate, alanine and lactate in the presence of valproate was much less from glutamate than from glutamine. Inhibition by amino-oxyacetate of accumulation of aspartate and alanine from glutamine caused by valproate did not prevent the acceleration of glutamine utilization and the subsequent stimulation of ammonia formation. These data are consistent with a stimulatory effect of valproate primarily exerted at the level of glutaminase in dog kidney tubules. However, the fact that assayed activity of glutaminase remained unchanged in the presence of valproate suggests that this compound accelerates flux through the latter enzyme by an indirect mechanism probably related to the renal metabolism of this compound.
...
PMID:Stimulation of glutamine metabolism by the antiepileptic drug, sodium valproate, in isolated dog kidney tubules. 257 76

15N kinetic labelling studies were done on liquid cultures of wild-type Aspergillus nidulans. The labelling pattern of major amino acids under 'steady state' conditions suggests that glutamate and glutamine-amide are the early products of ammonia assimilation in A. nidulans. In the presence of phosphinothricin, an inhibitor or glutamine synthetase, 15N labelling of glutamate, alanine and aspartate was maintained whereas the labelling of glutamine was low. This pattern of labelling is consistent with ammonia assimilation into glutamate via the glutamate dehydrogenase pathway. In the presence of azaserine, an inhibitor of glutamate synthase, glutamate was initially more highly labelled than any other amino acid, whereas its concentration declined. Isotope also accumulated in glutamine. Observations with these two inhibitors suggest that ammonia assimilation can occur concurrently via the glutamine synthetase/glutamate synthase and the glutamate dehydrogenase pathways in low-ammonia-grown A. nidulans. From a simple model it was estimated that about half of the glutamate was synthesized via the glutamate dehydrogenase pathway; the other half was formed from glutamine via the glutamate synthase pathway. The transfer coefficients of nine other amino acids were also determined.
...
PMID:Ammonia assimilation by Aspergillus nidulans: [15N]ammonia study. 257 37

One-step and two-step assay methods were developed for general aminotransferases (ATs) utilizing Glu and alpha-ketoglutarate (alpha-KG) as the donor and acceptor of the amino group, by coupling a glutamate dehydrogenase (GDH) reaction with the AT reactions. For instance, alpha-KG formed from Glu by AspAT is reduced and aminated back to Glu by GDH, which oxidizes NADPH corresponding to the amount of alpha-KG formed. In the reverse reaction, Glu formed from alpha-KG is oxidized and deaminated back to alpha-KG by GDH, which reduces NADP+ corresponding to the amount of Glu formed. In the one-step assay, both AT and GDH reactions are simultaneously carried out, and the decrease or increase in NADPH fluorescence is directly monitored in 1.0 ml of the reaction mixture for both forward and reverse reactions. In the two-step assay, an AT reaction is carried out and stopped once at the first step. Next, the alpha-KG or Glu formed is determined fluorometrically in a GDH reaction. In order to analyze partially purified or crude samples, the one-step assay is convenient for surveying the relative activities. The two-step assay is useful for analyzing the properties of enzymes and measuring activities under conditions approaching the optimum. AspAT can be replaced by other general ATs using enzyme-specific substrates in place of oxalacetate and Asp in the assay mixture. The present methods were successfully applied to four enzymes (Asp, alanine, gamma-aminobutyrate, and ornithine ATs) in tissue homogenates and a mitochondrial extract.
...
PMID:One-step and two-step fluorometric assay methods for general aminotransferases using glutamate dehydrogenase. 260 38

NADP+-specific glutamate dehydrogenase from Salmonella typhimurium, cloned and expressed in Escherichia coli, has been purified to homogeneity. The nucleotide sequence of S. typhimurium gdhA was determined and the amino acid sequence derived. The nucleotide analogue 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 2',5'-bisphosphate (2-BDB-T epsilon A-2',5'-DP) reacts irreversibly with the enzyme to yield a partially inactive enzyme. After about 60% loss of activity, no further inactivation is observed. The rate of inactivation exhibits a nonlinear dependence on 2-BDB-T epsilon A-2',5'-DP concentration with kmax = 0.160 min-1 and KI = 300 microM. Reaction of 200 microM 2-BDB-T epsilon A-2',5'-DP with glutamate dehydrogenase for 120 min results in the incorporation of 0.94 mol of reagent/mol of enzyme subunit. The coenzymes, NADPH and NADP+, completely protect the enzyme against inactivation by the reagent and decrease the reagent incorporation from 0.94 to 0.5 mol of reagent/mol enzyme subunit, while the substrate alpha-ketoglutarate offers only partial protection. These results indicate that 2-BDB-T epsilon A-2',5'-DP functions as an affinity label of the coenzyme binding site and that specific reaction occurs at only about 0.5 sites/enzyme subunit or 3 sites/hexamer. Glutamate dehydrogenase modified with 200 microM 2-BDB-T epsilon A-2',5'-DP in the absence and presence of coenzyme was reduced with NaB3H4, carboxymethylated, and digested with trypsin. Labeled peptides were purified by high performance liquid chromatography and characterized by gas phase sequencing. Two peptides modified by the reagent were isolated and identified as follows: Phe-Cys(CM)-Gln-Ala-Leu-Met-Thr-Glu-Leu-Tyr-Arg and Leu-Cys(CM)-Glu-Ile-Lys. These two peptides were located within the derived amino acid sequence as residues 146-156 and 282-286. In the presence of NADPH, which completely prevents inactivation, only peptide 146-156 was labeled. This result indicates that modification of the pentapeptide causes loss of activity. Glutamate 284 in this peptide is the probable reaction target and is located within the coenzyme binding site.
...
PMID:Affinity labeling of a glutamyl peptide in the coenzyme binding site of NADP+-specific glutamate dehydrogenase of Salmonella typhimurium by 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 2',5'-bisphosphate. 265 14

Both glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) are involved in glutamate synthesis in Streptomyces coelicolor. The highest levels of GDH were seen in extracts of cells grown with high levels of ammonium as the nitrogen source. GOGAT activity was reduced two- to threefold in extracts of cells grown with good sources of glutamate. S. coelicolor mutants deficient in GOGAT (Glt-) required glutamate for growth with L-alanine, asparagine, arginine, or histidine as the nitrogen source but grew like wild-type cells when ammonium, glutamine, or aspartate was the nitrogen source. The glt mutations were tightly linked to hisA1. Mutants deficient in both GOGAT and GDH (Gdh-) required glutamate for growth in all media. The gdh-5 mutation was mapped to the left region of the S. coelicolor chromosomal map, between proA1 and uraA1.
...
PMID:Glutamate synthesis in Streptomyces coelicolor. 270 9

Ethanol or acetaldehyde orally administered (15% and 2% respectively in drinking water) to male Wistar rats for three months induced alterations in the main liver enzymes responsible for ethanol metabolism, aspartate and alanine aminotransferases and NAD glutamate dehydrogenase. Ethanol produced a significant decrease in the activity of soluble alcohol dehydrogenase, while acetaldehyde induced alterations both in soluble and mitochondrial aldehyde dehydrogenases: soluble activity was significantly higher than in the control and ethanol-treated groups, and mitochondrial activity was significantly diminished. Both soluble aspartate and alanine aminotransferases showed pronounced increases by the chronic effect of acetaldehyde, while mitochondrial activities were practically unchanged by the effect of ethanol or acetaldehyde. Mitochondrial NAD glutamate dehydrogenase showed a rise in its activity both by the effect of chronic ethanol and acetaldehyde consumption. The level of metabolites assayed in liver extracts showed marked differences between ethanol and acetaldehyde treatment which indicates that ethanol produced a remarkable increase in glutamate, aspartate and free ammonia together with marked decrease in pyruvate and 2-oxoglutarate concentrations. Acetaldehyde consumption induced a significant decrease in 2-oxoglutarate and pyruvate concentrations. These observations suggest that ethanol has an important effect on the urea cycle enzymes, while the effect of acetaldehyde contributes to the impairment of the citric acid cycle.
...
PMID:Effect of chronic ethanol or acetaldehyde on hepatic alcohol and aldehyde dehydrogenases, aminotransferases and glutamate dehydrogenase. 286 Jul 5

To obtain information on the route(s) of ammonium assimilation in Streptomyces venezuelae, cell suspensions transferred to fresh medium lacking nitrogen were pulsed with [15N2]ammonium sulphate. Cells and extracellular fluids were examined by nuclear magnetic resonance and amino acid analysis to assess changes in amino acid pools and the disposition of [15N]ammonium. Following addition of [15N]ammonium, glutamate--glutamine pools of low cell density replacement cultures expanded rapidly and became progressively labelled with 15N, whereas the alanine pool size increased much more slowly and became labelled with 15N to a much lesser extent. These results are consistent with the assimilation of ammonium via glutamate dehydrogenase or glutamine synthetase--glutamate synthase rather than alanine dehydrogenase. Under anaerobic conditions, S. venezuelae assimilates ammonium into alanine rather than glutamate--glutamine. Alanine dehydrogenase may thus function as a vehicle to regenerate NAD+ to maintain substrate-level phosphorylation during periods of anaerobiosis.
...
PMID:Pathway of ammonium assimilation in Streptomyces venezuelae examined by amino acid analyses and 15N nuclear magnetic resonance spectroscopy. 286 83

Activity levels of the enzymes of glutamate metabolism were determined in the neuronal perikarya and synaptosomes isolated from the cerebral cortex of normal and hyperammonemic rats. In neuronal perikarya, the activities of glutamate dehydrogenase, aspartate, alanine aminotransferases and glutamine synthetase were elevated in hyperammonemic states. In synaptosomes, glutamate dehydrogenase and aspartate aminotransferase were suppressed, while glutamine synthetase and glutaminase were elevated. These results suggested the involvement of neuronal perikarya in ammonia detoxification at least in acute hyperammonemic states.
...
PMID:Differential response of enzymes of glutamate metabolism in neuronal perikarya and synaptosomes in acute hyperammonemia in rat. 286 71


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

---