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:1.4.1.2 (glutamate dehydrogenase)
4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The enzymes of the assimilation pathways in cultures of S. hygroscopicus grown in the presence of various nitrogen sources were investigated. No assimilation activity of glutamate dehydrogenase (GDH) was observed. Activities of alanine dehydrogenase (ADH), GDH, glutamine: 2-oxoglutarate aminotransferase (GOGAT) and glutamate synthetase (GS) were studied. High concentrations of ammonium and alanine induced ADH formation. The levels of GS remained low in media with NH4Cl. Various nitrogen sources had no impact on the activity of GOGAT which suggested the involvement of constitutive synthesis. ADH was likely to play an alternative role. Determination of the quantitative and qualitative composition of the free amino acids confirmed the involvement of the GS-GOGAT pathway in nitrogen assimilation. The concentration of ammonium ions in the media with one amino acid or in the presence of several amino acids lowered the antibiotic activity while in the media with alanine and the other nitrogen compounds it increased the antibiotic activity.
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PMID:[Impact of nitrogen assimilation on regulation of antibiotic production in Streptomyces hygroscopicus 155]. 187 81

The presence of peroxisomes and peroxisomal enzyme activities were investigated in the oleaginous yeast Apiotrichum curvatum ATCC 20509 (formerly Candida curvata D.) Catalase, a marker enzyme for peroxisomes, was measured in cell-free extracts prepared by sonication. The nature of the carbon and nitrogen sources in the growth medium greatly affected catalase activity. Cells grown on corn oil had high specific activity of catalase, but those grown on glucose, sucrose, or maltose had low specific activity. High specific activity of catalase was measured in cultures grown on media that supported poor growth (with soluble starch as carbon source or with methylamine, urea, or asparagine as nitrogen source). Peroxisomes from cells grown on corn oil were separated from other subcellular fractions in a discontinuous sucrose gradient. Major peaks of activity of fatty acid beta-oxidation and of two key enzymes in the glyoxylate cycle were found in fractions containing peroxisomes, but not in fractions corresponding to the mitochondria. Peroxisomal beta-oxidation showed equivalent activity with palmitoyl CoA or n-octanoyl CoA as substrate. Mitochondria did not seem to contain NAD-linked glutamate dehydrogenase. Peroxisomes with a homogeneous matrix and core surrounded by a single-layer membrane were observed with an electron microscope in cells grown on corn oil, but not in those grown on glucose. Staining with 3,3'-diaminobenzidine revealed that catalase activity was located in peroxisomes. Peroxisomes in this oleaginous yeast play important roles in lipid metabolism.
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PMID:Evidence of peroxisomes and peroxisomal enzyme activities in the oleaginous yeast Apiotrichum curvatum. 187 14

The present study utilized [15N]glutamine labeled at amide (5-N) and amino (2-N) groups to analyze the metabolic fate of glutamine nitrogen in basal and in acute pH regulation of ammoniagenesis. One-hour incubation of LLC-PK1 cultures in a media of pH 7.4, 7.0, or 7.6 containing either [5-15N]glutamine or [2-15N]glutamine resulted in parallel alterations in glutamine consumption in response to acute acid-base maneuvers. Incubation with [5-15N]glutamine resulted in substantial enrichment and production of ammonia at pH 7.4, which was unaffected by the changes in media pH, and in no significant enrichment of alanine, aspartate, and glutamate. In contrast, significant enrichment and production of 15N-labeled ammonia, alanine, aspartate, and glutamate were detected from cultures incubated with [2-15N]glutamine. Ammonia formation, from incubation with [2-15N]glutamine, was stimulated significantly by a low pH and inhibited by high pH. Alanine production was altered in a fashion similar to ammonia formation, whereas aspartate production was unaltered and glutamate formation significantly decreased by a low pH. Furthermore, a low pH significantly increased the production of alpha-ketoglutaramate in a fashion qualitatively similar to alanine production. In contrast to our prior conclusions based on total metabolite production, these studies indicate that although ammonia formation at pH 7.4 is predominantly generated from the mitochondrial phosphate-dependent glutaminase pathway, the increased ammonia formation in acute acidosis is a result of increased flux through glutamate dehydrogenase.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pathways of acute pH regulation of ammoniagenesis in LLC-PK1 cells: study with [15N]glutamine. 188 9

An NAD(P)-dependent glutamate dehydrogenase was purified to homogeneity from the thermoacidophilic archaebacterium Sulfolobus solfataricus. The enzyme is a hexamer (subunit mass 45 kDa) which dissociates into lower states of association when submitted to gel filtration. Isoelectric focusing analysis of the purified enzyme showed a pI of 5.7 and occasionally revealed microheterogeneity. The enzyme is strictly specific for the natural substrates 2-oxoglutarate and L-glutamate, but is active with both NADH and NADPH. S. solfataricus glutamate dehydrogenase revealed a high degree of thermal stability (at 80 C the half-life was 15 h) which was strictly dependent on the protein concentration. Very high levels of glutamate dehydrogenase were found in this archaebacterium which suggests that the conversion of 2-oxoglutarate and ammonia to glutamate is of central importance to the nitrogen metabolism in this bacterium.
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PMID:Glutamate dehydrogenase from the thermoacidophilic archaebacterium Sulfolobus solfataricus. 190 Oct 40

Changes in hepatopancreas, muscle and gill tissue nitrogen metabolic profiles were studied in a penaeid prawn, Penaeus indicus, following its exposure to sublethal concentrations of methylparathion, carbaryl and aldrin. In all the insecticide exposed prawn tissues, Ammonia levels were significantly increased and a shift in the nitrogen metabolism towards the synthesis of urea and glutamine was observed. Inhibition of glutamate oxidation to ammonia and alpha-ketoglutarate by glutamate dehydrogenase suggests a mechanism whereby hyperammonemia is reduced by minimizing the addition of further ammonia to the already existing elevated ammonia pool. Increased alanine and aspartate aminotransferases demonstrates the onset of gluconeogenesis. Mechanisms to detoxify the ammonia by enhancing the synthesis of urea and glutamine at the cellular level was observed in the selected tissues pave way for the survivability of prawns in insecticide polluted environs.
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PMID:Methylparathion, carbaryl and aldrin impact on nitrogen metabolism of prawn, Penaeus indicus. 190 40

Frankia spp. are filamentous actinomycetes that fix N2 in culture and in actinorhizal root nodules. In combined nitrogen-depleted aerobic environments, nitrogenase is restricted to thick-walled spherical structures, Frankia vesicles, that are formed on short stalks along the vegetative hyphae. The activities of the NH4(+)-assimilating enzymes (glutamine synthetase [GS], glutamate synthase, glutamate dehydrogenase, and alanine dehydrogenase) were determined in cells grown on NH4+ and N2 and in vesicles and hyphae from N2-fixing cultures separated on sucrose gradients. The two frankial GSs, GSI and GSII, were present in vesicles at levels similar to those detected in vegetative hyphae from N2-fixing cultures as shown by enzyme assay and two-dimensional polyacrylamide gel electrophoresis. Glutamate synthase, glutamate dehydrogenase, and alanine dehydrogenase activities were restricted to the vegetative hyphae. Vesicles apparently lack a complete pathway for assimilating ammonia beyond the glutamine stage.
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PMID:Enzymes of ammonia assimilation in hyphae and vesicles of Frankia sp. strain CpI1. 196 54

We cloned GDH2, the gene that encodes the NAD-linked glutamate dehydrogenase in the yeast Saccharomyces cerevisiae, by purifying the enzyme, making polyclonal antibodies to it, and using the antibodies to screen a lambda gt11 yeast genomic library. A yeast strain with a deletion-disruption allele of GDH2 which replaced the wild-type gene grew very poorly with glutamate as a nitrogen source, but growth improved significantly when the strain was also provided with adenine or other nitrogenous compounds whose biosynthesis requires glutamine. Our results indicate that the NAD-linked glutamate dehydrogenase catalyzes the major, but not sole, pathway for generation of ammonia from glutamate. We also isolated yeast mutants that lacked glutamate synthase activity and present evidence which shows that normally NAD-linked glutamate dehydrogenase is not involved in glutamate biosynthesis, but that if the enzyme is overexpressed, it may function reversibly in intact cells.
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PMID:Role of NAD-linked glutamate dehydrogenase in nitrogen metabolism in Saccharomyces cerevisiae. 197 78

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 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


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