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

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Query: EC:1.4.1.4 (glutamate dehydrogenase)
4,358 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A positive, genetic selection against the activity of the nitrogen regulatory (NTR) system was used to isolate insertion mutations affecting nitrogen regulation in Klebsiella aerogenes. Two classes of mutation were obtained: those affecting the NTR system itself and leading to the loss of almost all nitrogen regulation, and those affecting the nac locus and leading to a loss of nitrogen regulation of a family of nitrogen-regulated enzymes. The set of these nac-dependent enzymes included histidase, glutamate dehydrogenase, glutamate synthase, proline oxidase, and urease. The enzymes shown to be nac independent included glutamine synthetase, asparaginase, tryptophan permease, nitrate reductase, the product of the nifLA operon, and perhaps nitrite reductase. The expression of the nac gene was itself highly nitrogen regulated, and this regulation was mediated by the NTR system. The loss of nitrogen regulation was found in each of the four insertion mutants studied, showing that loss of nitrogen regulation resulted from the absence of nac function rather than from an altered form of the nac gene product. Thus we propose two classes of nitrogen-regulated operons: in class I, the NTR system directly activates expression of the operon; in class II, the NTR system activates nac expression and the product(s) of the nac locus activates expression of the operon.
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PMID:Role of the nac gene product in the nitrogen regulation of some NTR-regulated operons of Klebsiella aerogenes. 197 23

The expression patterns of the mRNAs for the ammonia-metabolizing enzymes carbamoylphosphate synthetase (CPS), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) were studied in developing pre- and neonatal rat liver by in situ hybridization. In the period of 11 to 14 embryonic days (ED) the concentrations of GS and GDH mRNA increases rapidly in the liver, whereas a substantial rise of CPS mRNA in the liver does not occur until ED 18. Hepatocyte heterogeneity related to the vascular architecture can first be observed at ED 18 for GS mRNA, at ED 20 for GDH mRNA and three days after birth for CPS mRNA. The adult phenotype is gradually established during the second neonatal week, i.e. GS mRNA becomes confined to a pericentral compartment of one to two hepatocytes thickness, CPS mRNA to a large periportal compartment being no longer expressed in the pericentral compartment and GDH mRNA is expressed over the entire porto-central distance, decreasing in concentration going from central to portal. Comparison of the observed mRNA distribution patterns in the perinatal liver, with published data on the distribution of the respective proteins, points to the occurrence of posttranslational, in addition to pretranslational control mechanisms in the period of ontogenesis of hepatocyte heterogeneity. Interestingly, during development all three mRNAS are expressed outside the liver to a considerable extent and in a highly specific way, indicating that several organs are involved in the developmentally regulated expression of the mRNAs for the ammonia-metabolizing enzymes, that were hitherto not recognized as such.
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PMID:Expression patterns of mRNAs for ammonia-metabolizing enzymes in the developing rat: the ontogenesis of hepatocyte heterogeneity. 197 81

It has been found that there exists a correlation in the dynamics of changes in the amount of glutamate, alpha-ketoglutarate, glutamine, ammonia and activity level or alpha-ketoglutarate dehydrogenase, NADP-glutamate dehydrogenase, glutamine synthetase and glutaminase in the brain of young carp in the process of winter starvation. It has been stated that under condition of energy deficiency and meaningful amount of ammonia in the organism of hibernating fish, its binding parallel with the known glutamine synthetase mechanism may proceed in the course of the NADP-glutamate dehydrogenase reaction which balance is shifted towards the glutamate synthesis. This reaction is supposed to provide the outflow of alpha-ketoglutarate from the citric cycle, which intensifies energy deficiency of the organism.
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PMID:[Features of the interconversion of alpha-ketoglutarate--glutamate in brain mitochondria of exothermic animals during hibernation]. 198 77

The URE2 gene of Saccharomyces cerevisiae has been cloned and sequenced. It encodes a predicted polypeptide of 354 amino acids with a molecular weight of 40,226. Deletion of the first 63 amino acids does not have any effect on the function of the protein. Studies with disruption alleles of the URE2 and GLN3 genes showed that both genes regulate GLN1 and GDH2, the structural genes for glutamine synthetase and NAD-linked glutamate dehydrogenase, respectively, at the transcriptional level, but expression of the regulatory genes does not appear to be regulated. Active URE2 gene product was required for the inactivation of glutamine synthetase upon addition of glutamine to cells growing with glutamate as the source of nitrogen. The predicted URE2 gene product has homology to glutathione S-transferases. The gene has been mapped to chromosome XIV, 5.9 map units from petX and 3.4 map units from kex2.
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PMID:The URE2 gene product of Saccharomyces cerevisiae plays an important role in the cellular response to the nitrogen source and has homology to glutathione s-transferases. 199 Feb 86

Viable toadfish hepatocytes were separated into distinct subpopulations by gradient centrifugation. Although 3-5 density subpopulations were obtained for each fish, only two metabolically and enzymatically different subpopulations could be discerned. In all cases, hepatocytes with the lowest density (less than 1.040 g ml-1) were more oxidative in scope, as judged by the activities of mitochondrial enzymes (citrate synthase, aspartate aminotransferase, glutamate dehydrogenase); activities of these enzymes (normalised to cell protein) were on average two- to threefold higher than in subpopulations with higher densities. Lower-density hepatocytes also contained higher levels of the urea cycle enzymes arginase and ornithine carbamoyltransferase. The higher-density subpopulations showed no significant differences from each other in enzymatic activities. Compared with lower-density cells, these hepatocytes had higher activities of two cytosolic enzymes, malate dehydrogenase and glutathione-S-transferase. There was no distinct distribution pattern for alanine aminotransferase and glutamine synthetase. Despite generally lower oxidative enzyme content, higher-density hepatocytes were metabolically more active, with 2.5- to fourfold higher rates of urea synthesis, gluconeogenesis and oxidation of lactate. We conclude that, although the toadfish liver shows distinct enzymatic and metabolic heterogeneity, this heterogeneity is dissimilar to the zonation pattern in the livers of mammals, in that separated toadfish hepatocyte types did not appear to possess exclusive metabolic functions. Notably, all cells were capable of metabolic functions that are strictly localised in mammalian liver. In nitrogen metabolism, glutamine synthetase displays a distribution pattern commensurate with its unique metabolic function in the liver of the ureogenic toadfish. Further, all subpopulations possessed detoxification capabilities as indicated by high levels of glutathione-S-transferase, a 'phase II' conjugation enzyme.
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PMID:Metabolic and enzymatic heterogeneity in the liver of the ureogenic teleost Opsanus beta. 205 Nov 31

It is well known that brain function is critically dependent upon energy metabolism and that the brain has a relatively high metabolic rate. Experiments using intact brain preparations do not provide information about metabolism in the different cell types that constitute brain tissue. Progress in primary culture techniques has facilitated biochemical investigations and analysis of the metabolic pathways prevailing in specific cerebral cell types. We found that, in the presence of pyruvate or succinate as the substrate, oxygen consumption by neurons grown in culture was always higher than that by glial cells. The relatively low values of hexokinase, malate dehydrogenase and glutamate dehydrogenase activities observed in glial cells and, in contrast, the high levels of lactate dehydrogenase and enolase activities may be the result of a less aerobic metabolism prevailing in this type of brain cell, compared to neurons. On the other hand, the predominance of the aerobic, lactate dehydrogenase, isoenzymatic form in neurons can be associated with a more aerobic metabolism in this type of cell. In the case of severe hypoxia, we observed that astrocytes were the most damaged cells. An increased lactate dehydrogenase level with a modification of its isoenzymatic profile and a decreased glutamine synthetase activity under hypoxic conditions indicated severe derangement of important biochemical functions within the astrocytes. By antagonizing some of these changes, almitrine and raubasine (both present in Duxil) seem to exert some protective effect. One may consider that, among the different cell types present in brain tissue, astroglial cells may represent a target particularly sensitive to hypoxia-induced injury.
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PMID:[Neuronal and astrocytic plasticity: metabolic aspects]. 208 81

Evidence for the existence of a glutamine cycle in Neurospora crassa is reviewed. Through this cycle glutamine is converted into glutamate by glutamate synthase and catabolized by the glutamine transaminase-omega-amidase pathway, the products of which (2-oxoglutarate and ammonium) are the substrates for glutamate dehydrogenase-NADPH, which synthesizes glutamate. In the final step ammonium is assimilated into glutamine by the action of a glutamine synthetase (GS), which is formed by two distinct polypeptides, one catalytically very active (GS beta), and the other (GS alpha) less active but endowed with the capacity to modulate the activity of GS alpha. Glutamate synthase uses the amide nitrogen of glutamine to synthesize glutamate; glutamate dehydrogenase uses ammonium, and both are required to maintain the level of glutamate. The energy expended in the synthesis of glutamine drives the cycle. The glutamine cycle is not futile, because it is necessary to drive an effective carbon flow to support growth; in addition, it facilitates the allocation of nitrogen or carbon according to cellular demands. The glutamine cycle which dissipates energy links catabolism and anabolism and, in doing so, buffers variations in the nutrient supply and drives energy generation and carbon flow for optimal cell function.
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PMID:Glutamine metabolism and cycling in Neurospora crassa. 214 4

1. Glutamine was found to be the main carbon and nitrogen product of the metabolism of aspartate in isolated guinea-pig kidney-cortex tubules. Glutamate, ammonia and alanine were only minor products. 2. Carbon-balance calculations and the release of 14CO2 from [U-14C]aspartate indicate that oxidation of the aspartate carbon skeleton occurred. 3. A pathway involving aspartate aminotransferase, glutamate dehydrogenase, glutamine synthetase, phosphoenolpyruvate carboxykinase, pyruvate kinase, pyruvate dehydrogenase and enzymes of the tricarboxylic acid cycle is proposed for the conversion of aspartate into glutamine. 4. Evidence for this pathway was obtained by: (i) inhibiting aspartate removal by amino-oxyacetate, an inhibitor of transaminases, (ii) the use of methionine sulphoximine, an inhibitor of glutamine synthetase, which induced a large increase in ammonia release from aspartate, (iii) the use of quinolinate, an inhibitor of phosphoenolpyruvate carboxykinase, which inhibited glutamine synthesis from aspartate, (iv) the use of alpha-cyano-4-hydroxycinnamate, an inhibitor of the mitochondrial transport of pyruvate, which caused an accumulation of pyruvate from aspartate, and (v) the use of fluoroacetate, an inhibitor of aconitase, which inhibited glutamine synthesis with concomitant accumulation of citrate from aspartate.
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PMID:Glutamine synthesis from aspartate in guinea-pig renal cortex. 236 82

The activities of alanine-, aspartate- and branched-chain amino-acid transaminases, glutamine synthetase, glutamate dehydrogenase and adenylate deaminase in white adipose tissue of adult male rats have been determined in animals submitted to 12-h cold exposure (4 degrees C) or to 24-h food deprivation. Starvation resulted in small changes in glutamate dehydrogenase and alanine transaminase when expressed per unit of protein weight, inducing an increase in branched-chain amino-acid transaminase and glutamine synthetase. Cold exposure showed the same effects as starvation with respect to glutamate dehydrogenase and alanine transaminase, but induced increases in glutamine synthetase and aspartate transaminase. It is concluded that starvation increases the handling of some amino acids by white adipose tissue and the detoxification of the ammonia thus evolved. The changes observed suggest a different pattern of amino-acid metabolism enzyme changes with either cold or starvation.
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PMID:Amino-acid metabolism enzyme activities in rat white adipose tissue. 243 May 32

To contribute to our understanding of nitrogen metabolism in the developing chick we have studied in liver, intestine and yolk sac membrane the ontogeny of both aspartate- and alanine transaminases, glutamate dehydrogenase, adenylate deaminase, glutamine synthetase and xanthine dehydrogenase activities. Liver enzyme activities were much higher than those of the same enzymes in intestine and yolk sac membrane, the latter having the lowest activities. In the liver, both alanine transaminase and glutamate dehydrogenase increased their activity just before hatching, xanthine dehydrogenase and glutamine synthetase develop their highest activity just after hatching, while aspartate transaminase and adenylate deaminase attained the highest levels just with adulthood. From the pattern of enzyme activity in yolk sac membrane and intestine it can be inferred that after hatching, the amino-acid metabolism in these tissues is considerably enhanced, with higher production of ammonia from amino acids, as indicated by the rise in adenylate deaminase, as well as increased potentiality in production of both alanine and glutamine. It can be concluded that hatching coincides with a deep change of pace in amino-acid metabolism in the organs studied fully comparable with that observed in Mammals at the end of lactation, with the difference that the adaptation to the new diet in the case of the chick is much more sudden than weaning is for the rat.
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PMID:Amino-acid metabolism enzyme activities in the liver, intestine and yolk sac membrane of developing domestic fowl. 243 52


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