Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.4.3.11 (glutamate dehydrogenase)
 4,437 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relationship between nitrogen assimilation, metabolism and aflatoxin formation has been investigated in a toxigenic and a non-toxigenic strain of Aspergillus parasiticus. Ammonia from the medium is mainly assimilated via NADP-requiring glutamate dehydrogenase. During growth NAD-requiring glutamate dehydrogenase followed an inverse pattern of activity with respect to NADP glutamate dehydrogenase. Alpha-ketoglutarate, the product of NAD glutamate dehydrogenase, stimulated acetate incorporation into aflatoxins. Glutamine synthetase, ornithine transcarbamylase, both utilizing glutamate as substrate were assayed under different growth conditions. An important regulatory role for glutamine synthetase is suggested. The metabolic route of asparagine utilization was also investigated. Both the known pathways, glutamate oxaloacetate transaminase and glutamate pyruvate transaminase are operative simultaneously.
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PMID:Nitrogen metabolism in Aspergillus parasiticus NRRL 3240 and A. flavus NRRL 3537 in relation to aflatoxin production. 287 96

The mitochondria isolated from transplantable chicken hepatomatous growth induced by MC-29 virus were deficient in glutamate dehydrogenase. Oxypolarographic tests showed that glutamate oxidation in the tumor mitochondria was initiated via transamination, while glutamate was deaminated by glutamate dehydrogenase in liver mitochondria to supply adenosine triphosphate. Prominent glutamate oxidation and transformation-linked low glutamine synthetase activity may be favorable to the bioenergetics of this fast-growing tumor.
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PMID:The pathway of glutamate oxidation in isolated mitochondria from the avian hepatomatous growth induced by MC-29 virus. 287 70

The short-term metabolic fate of [13N]ammonia in the livers of adult male, anesthetized rats was determined. Following a bolus injection of tracer quantities of [13N]ammonia into the portal vein, the single pass extraction was approximately 93%, in good agreement with the portal-hepatic vein difference of approximately 90%. High performance liquid chromatographic analysis of deproteinized liver samples indicated that labeled nitrogen is exchanged rapidly among components of: mitochondrial aspartate aminotransferase and glutamate dehydrogenase reactions and cytoplasmic aspartate aminotransferase and alanine aminotransferase reactions (t1/2 for the exchange of label toward equilibrium is on the order of seconds). Comparison of specific activities of glutamate and ammonia suggests that at 5 s most labeled glutamate was mitochondrial, whereas at 60 s approximately 93% was cytosolic; this change is presumably brought about by the combined action of the mitochondrial and cytosolic aspartate aminotransferases and the aspartate carrier of the malate-aspartate shuttle. Specific activity measurements of glutamate, alanine, and aspartate are in accord with the proposal by Williamson et al. (Williamson, D.H., Lopes-Vieira, O., and Walker, B. (1967) Biochem. J. 104, 497-502) that the components of the aspartate aminotransferase reaction are in thermodynamic equilibrium, whereas the components of the alanine aminotransferase reaction are in equilibrium but compartmented in the rat liver. Despite considerable label in citrulline at early time points, no radioactivity (less than or equal to 0.25% of the total) was detected in carbamyl phosphate, suggesting very efficient conversion to citrulline with little free carbamyl phosphate accumulating in the mitochondria. Our data also show that some portal vein-derived ammonia is metabolized to glutamine in the rat liver, but the amount is small (approximately 7% of that metabolized to urea) in part because liver glutamine synthetase is located in a small population of perivenous cells "downstream" from the urea cycle-containing periportal cells. Finally, no tracer evidence could be found for the participation of the purine nucleotide cycle in ammonia production from aspartate. The present work continues to emphasize the usefulness of [13N]ammonia for short-term metabolic studies under truly tracer conditions, particularly when turnover times are on the order of seconds.
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PMID:Short-term metabolic fate of [13N]ammonia in rat liver in vivo. 287 38

A glutamate auxotroph was obtained in Nostoc muscorum by induced mutagenesis with nitrosoguanidine. The metabolic pathway leading to glutamate synthesis was traced by selecting several enzymes. The strain was found to be lacking glutamate dehydrogenase. Other enzymes, however, were normal in their activity including isocitric dehydrogenase, glutamine synthetase and glutamate synthase. Nitrogen metabolism of the auxotroph and wild type was compared. The strain released exceedingly high amounts of ammonium in the medium.
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PMID:Regulation of glutamate dehydrogenase activity and ammonia production in a nitrogen fixing cyanobacterium. 288 Apr 48

The effect of 24-hr starvation on the amino acid pool composition and its concentration ratios with respect to blood and plasma as well as the activities of alanine, aspartate and branched chain amino acid transaminases, glutamate dehydrogenase, glutamine synthetase and adenylate deaminase have been studied in rat brown adipose tissue. Starvation induced a considerable decrease of pool amino acid concentration. Alanine and taurine were the amino acids in which the decrease was more marked. Small changes were observed in the activities of the enzymes studied, with decreases only in glutamate dehydrogenase and adenylate deaminase. These changes agree with a decrease in amino acid utilization in this tissue induced by starvation.
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PMID:Effect of 24-hour starvation on amino acid pool composition and enzyme activities of rat brown adipose tissue. 288 93

Pathways of ammonia assimilation into glutamic acid and alanine in Bacillus polymyxa were investigated by 15N NMR spectroscopy in combination with measurements of the specific activities of glutamate dehydrogenase, glutamine synthetase, glutamate synthetase, alanine dehydrogenase, and glutamic-alanine transaminase. Ammonia was found to be assimilated into glutamic acid predominantly by NADPH-dependent glutamate dehydrogenase with a Km of 2.9 mM for NH4+ not only in ammonia-grown cells but also in nitrate-grown and nitrogen-fixing cells in which the intracellular NH4+ concentrations were 11.2, 1.04, and 1.5 mM, respectively. In ammonia-grown cells, the specific activity of alanine dehydrogenase was higher than that of glutamic-alanine transaminase, but the glutamate dehydrogenase/glutamic-alanine transaminase pathway was found to be the major pathway of 15NH4+ assimilation into [15N]alanine. The in vitro specific activities of glutamate dehydrogenase and glutamine synthetase, which represent the rates of synthesis of glutamic acid and glutamine, respectively, in the presence of enzyme-saturating concentrations of substrates and coenzymes are compared with the in vivo rates of biosynthesis of [15N]glutamic acid and [alpha,gamma-15N]glutamine observed by NMR, and implications of the results for factors limiting the rates of their biosynthesis in ammonia- and nitrate-grown cells are discussed.
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PMID:Ammonia assimilation in Bacillus polymyxa. 15N NMR and enzymatic studies. 288 2

A rapid enzymatic assay method for ammonia was developed by using glutamine synthetase from glutamate-producing bacteria together with pyruvate kinase, lactate dehydrogenase, and NADH. The time required for determination of 25 nmol of ammonia was 5 min with 1 unit of glutamine synthetase, as opposed to 14-30 min with 1 unit of glutamate dehydrogenases from various sources. The present method was used to determine ammonia in serum, microbiol-culture broth, and waste water. The method can be modified for spectrophotometry in the visible region by substituting pyruvate oxidase, peroxidase, and appropriate chromogens for lactate dehydrogenase and NADH. With 4-aminoantipyrine (4AA) and phenol, and with 4AA and N-ethyl-N-2-hydroxyethyl-m-toluidine as chromogens, the sensitivity of ammonia determination was 0.65 and 1.7 times that with glutamate dehydrogenase, respectively. The present method was also applicable to the continuous detection of the activity of some ammonia-forming enzymes such as guanase, adenosine deaminase, and urease and to the determination of 0.5-30 microM ATP-ADP after some modification of the mixture.
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PMID:A rapid assay method for ammonia using glutamine synthetase from glutamate-producing bacteria. 288 29

The amino acid pool composition and its concentration ratios with respect to blood and plasma, as well as the activities of alanine, aspartate and branched chain amino acid transaminases, glutamine synthetase, adenylate deaminase and glutamate dehydrogenase have been studied in the interscapular brown adipose tissue of control, 12-h cold-exposed and 15-day cold-acclimated rats. Cold temperature affected the amino acid metabolism and pool composition more intensely after 15 days than after 12-h cold-exposure, even though the patterns of change were very similar in both groups. Cold temperatures induced a decrease in glutamine and an increase in glutamate concentration in the tissue. This probably increased the metabolism of branched chain amino acids and caused a decrease in adenylate deaminase activity. It also seemed to increase alanine utilization. We concluded that amino acid metabolism in brown adipose tissue is enhanced by cold temperature acclimation.
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PMID:Effect of cold-temperature exposure and acclimation on amino acid pool changes and enzyme activities of rat brown adipose tissue. 288 9

The specific activities of glutamine synthetase (GS) and glutamate synthase (GOGAT) were 4.2- and 2.2-fold higher, respectively, in cells of Azospirillum brasilense grown with N2 than with 43 mM NH4+ as the source of nitrogen. Conversely, the specific activity of glutamate dehydrogenase (GDH) was 2.7-fold higher in 43 mM NH4+-grown cells than in N2-grown cells. These results indicate that NH4+ could be assimilated and that glutamate could be formed by either the GS-GOGAT or GDH pathway or both, depending on the cellular concentration of NH4+. The routes of in vivo synthesis of glutamate were identified by using 13N as a metabolic tracer. The products of assimilation of 13NH4+ were, in order of decreasing radioactivity, glutamine, glutamate, and alanine. The formation of [13N]glutamine and [13N]glutamate by NH4+-grown cells was inhibited in the additional presence of methionine sulfoximine (an inhibitor of GS) and diazooxonorleucine (an inhibitor of GOGAT). Incorporation of 13N into glutamine, glutamate, and alanine decreased in parallel in the presence of carrier NH4+. These results imply that the GS-GOGAT pathway is the primary route of NH4+ assimilation by A. brasilense grown with excess or limiting nitrogen and that GDH has, at best, a minor role in the synthesis of glutamate.
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PMID:Assimilation of 13NH4+ by Azospirillum brasilense grown under nitrogen limitation and excess. 288 45

Brain ammonia is generated from many enzymatic reactions, including glutaminase, glutamate dehydrogenase, and the purine nucleotide cycle. In contrast, the brain possesses only one major enzyme for the removal of exogenous ammonia, i.e., glutamine synthetase. Thus, following administration of [13N]ammonia to rats [via either the carotid artery or cerebrospinal fluid (csf)], most metabolized label was in glutamine (amide) and little was in glutamate (plus aspartate). Since blood-and csf-borne ammonia are converted to glutamine largely, if not entirely, in the astrocytes, it is not possible from these types of experiments to predict with certainty the metabolic fate of the bulk of endogenously produced ammonia. By comparing the specific activity of L-[13N]glutamate to that of L-[amine-13N]glutamine following intracarotid [13N]ammonia administration it was concluded that metabolic compartmentation is no longer intact in the brains of rats treated with the glutamine synthetase inhibitor L-methionine-SR-sulfoximine (MSO) and that blood and brain ammonia pools mix in such animals. In MSO-treated animals, recovery of label in brain was low (approximately 20% of controls), and of the label remaining, a prominent portion was in glutamine (amide) (despite an 87% decrease in brain glutamine synthetase activity). These data are consistent with the hypothesis that glutamine synthetase is the major enzyme for metabolism of endogenously--as well as exogenously--produced ammonia. The rate of turnover of blood-derived ammonia to glutamine in normal rat brain is extremely rapid (t1/2 less than or equal to 3 s), but is slowed in the brains of chronically (12-14-wk portacaval-shunted) or acutely (urease-treated) hyperammonemic rats (t1/2 less than or equal to 10 s). The slowed turnover rate may be caused by an increased astrocytic ammonia, decreased glutamine synthetase activity, or both. In the hyperammonemic rat brain, glutamine synthetase is still the only important enzyme for the removal of blood-borne ammonia. Hyperammonemia causes an increase in brain lactate/pyruvate ratios and decreases in brain glutamate and brainstem ATP, consistent with an interference with the malate-aspartate shuttle. In vitro, pathological levels of ammonia also inhibit brain alpha-ketoglutarate dehydrogenase complex and, less strongly, pyruvate dehydrogenase complex. The rat brain does not adapt to prolonged hyperammonemia by increasing its glutamine synthetase activity.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Cerebral ammonia metabolism in normal and hyperammonemic rats. 288 66


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