Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P17174 (aspartate aminotransferase)
 14,872 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study belongs to a series of comparative biochemical and semiquantitative-histological investigations in renal tissue fractions of pyelonephritis patients (human PN) and of different types of experimental pyelonephritis (experimental PN). The experiments aim at more detailed knowledge on the interrelationship of intermediary cell metabolism and histopathological changes during the different phases of human and experimental PN. The results concerning acid and alkaline phosphatase activities as well as concerning glutaminase I and glutamic dehydrogenase activities were earlier reported (Exp. Path. vols. 8, 9, 10 and 12). In the present study the author has analyzed the activities of aspartate aminotransferase (E.C.2.6.1.1. AspAT) the synonym of which is glutamic oxaloacetic transaminase (GOT).
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PMID:[Aspartate aminotransferase activities in renal tissue during experimental and human chronic pyelonephritis]. 92 89

The possible involvement of ionotropic and metabotropic quisqualate (QA) receptors in neuronal plasticity was studied in cultured glutamatergic cerebellar or hippocampal cells in terms of the specific activity of phosphate-activated glutaminase, an enzyme important in the synthesis of the putative neurotransmitter pool of glutamate. When cerebellar or hippocampal neurons were treated with QA, it elevated the specific activity of glutaminase in a dose-dependent manner. The half-maximal effect was obtained at about 0.1 microM, the maximum increase was at about 1 microM, but levels higher than 10 microM QA produced progressive reduction in glutaminase activity. In contrast, QA had little effects on the activities of lactate dehydrogenase and aspartate aminotransferase and the amount of protein, indicating that the increase in glutaminase was relatively specific. The QA-mediated increase in glutaminase was mimicked by the ionotropic QA receptor agonist alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA; EC50, about 0.5 microM), but not by the metabotropic QA receptor agonist trans-(+-)-1-amino-cyclopentyl-1,3,dicarboxylate (t-ACPD; up to 0.5 mM). The specific ionotropic QA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) inhibited QA- and AMPA-mediated increases in glutaminase activity in a dose-dependent manner, whereas other glutamate receptor antagonists, D,L-2-amino-5-phosphonovalerate, gamma-D-glutamyl aminomethyl sulphonic acid and gamma-D-glutamyl diethyl ester were ineffective. The elevation of neurotransmitter enzyme was Ca(2+)-dependent.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of neurotransmitter enzyme by quisqualate subtype glutamate receptors in cultured cerebellar and hippocampal neurons. 133 Feb 9

Amino acid metabolism was examined in mitochondria from the lateral red muscle of a teleost (lake char, Salvelinus namaycush) and a nonteleost fish (bowfin, Amia calva). Isolated mitochondria oxidize a wide variety of substrates and have high respiratory control ratios. In both species, glutamine is oxidized more rapidly than any other amino acid. The rate of glutamine oxidation by bowfin mitochondria exceeds that of lake char mitochondria, and the bowfin displays correspondingly higher levels of mitochondrial phosphate-dependent glutaminase. It is suggested that amino acids in general, and glutamine in particular, are important oxidative substrates for nonteleost red muscle. The teleost red muscle, however, may rely on both glutamine and fatty acids as oxidative substrates. It appears that glutamate derived from glutamine is oxidized primarily via glutamate dehydrogenase, whereas exogenous glutamate is oxidized primarily via aspartate aminotransferase. Complete oxidation of glutamine may be accomplished in the absence of other substrates by conversion of glutamine-derived malate to pyruvate via malic enzyme. To assess the relative abilities of various tissues to synthesize and oxidize glutamine, the activities of glutamine synthetase and glutaminase were measured. The results of these studies indicate that the organization of glutamine metabolism of fish differs markedly from that in mammals.
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PMID:Glutamine metabolism in a holostean (Amia calva) and teleost fish (Salvelinus namaycush). 167 42

The possible involvement of quinolinic acid in the biochemical differentiation of cultured glutamatergic cerebellar granule neurons was studied in terms of the activity of phosphate-activated glutaminase (GLNase) and aspartate aminotransferase (ASP-AT). Treatment with quinolinate elevated the specific activity of GLNase and amount of protein per culture dish in a dose-dependent manner. The half maximal effect was obtained at about 0.5 mM quinolinate, whereas the maximum concentration, which produced about a 2.3-fold increase in GLNase activity, was about 2 mM. Quinolinate, like N-methyl-D-aspartate (NMDA), had no significant effects on the activities of ASP-AT and lactate dehydrogenase enzymes. The increases in the activity of GLNase and amount of protein were completely blocked by the NMDA receptor antagonist, 2-amino-5-phosphonovaleric acid. The result would indicate that, (a) contrary to an earlier proposal, ASP-AT does not appear to be a good marker for studying dynamic responses of glutamatergic neurons, and (b) the trophic effect of quinolinic acid on the development of cerebellar granule neurons is mediated by selective activation of NMDA subtype excitatory amino acid receptors.
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PMID:Quinolinic acid promotes the biochemical differentiation of cerebellar granule neurons. 214 31

The possible involvement of N-methyl-D-aspartate (NMDA) receptors in the biochemical differentiation of cultured neurons derived from the medial frontal part of the forebrain containing the septum-diagonal band region was studied in terms of the activities of enzymes important in the synthesis of neurotransmitter compounds. The activity of choline acetyltransferase (ChAT) was used as a marker for cholinergic neurons, glutamate decarboxylase (GAD) for GABAergic neurons and phosphate-activated glutaminase (GLNase) and aspartate aminotransferase (ASP-AT) for glutamatergic neurons, while lactate dehydrogenase (LDH) was included as an ubiquitous enzyme. The exposure of cultures to a depolarizing concentration of K+ (40 mM) for the last 3 days (i.e. between 2 and 5 days in vitro) significantly enhanced the expression of ChAT, GAD and GLNase activities, but high K+ caused little alteration in the activities of ASP-AT and LDH. On the other hand, treatment with NMDA markedly elevated the specific activities of GAD and GLNase only, and the compound had no significant effects on the activities of ChAT, ASP-AT and LDH enzymes. The enhancements of the specific activities of GAD and GLNase were completely blocked by the NMDA receptor antagonist, 2-amino-5-phosphonovaleric acid, and by the NMDA receptor-linked Ca2+ ion channel blocker, MK-801. On the basis of the present findings it is concluded that, (a) contrary to an earlier proposal, ASP-AT does not appear to be a good marker for the glutamatergic neurons, (b) the failure of the subcortical cholinergic neurons to respond by an increase in ChAT activity to NMDA may indicate that these nerve cells lack NMDA subtype excitatory amino acid receptors, and (c) as the septal GABAergic input in the hippocampus is involved in the modulation of long-term potentiation, the presence of NMDA receptors on these neurons would now suggest that NMDA receptors are linked to both the initiation and the modulation of hippocampal plasticity in the mammalian brain.
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PMID:Cell-type specific effects of N-methyl-D-aspartate on biochemical differentiation of subcortical neurons in culture. 214 34

Energy metabolism in proliferating cultured rat thymocytes was compared with that of freshly prepared non-proliferating resting cells. Cultured rat thymocytes enter a proliferative cycle after stimulation by concanavalin A and Lymphocult T (interleukin-2), with maximal rates of DNA synthesis at 60 h. Compared with incubated resting thymocytes, glucose metabolism by incubated proliferating thymocytes was 53-fold increased; 90% of the amount of glucose utilized was converted into lactate, whereas resting cells metabolized only 56% to lactate. However, the latter oxidized 27% of glucose to CO2, as opposed to 1.1% by the proliferating cells. Activities of hexokinase, 6-phosphofructokinase, pyruvate kinase and aldolase in proliferating thymocytes were increased 12-, 17-, 30- and 24-fold respectively, whereas the rate of pyruvate oxidation was enhanced only 3-fold. The relatively low capacity of pyruvate degradation in proliferating thymocytes might be the reason for almost complete conversion of glucose into lactate by these cells. Glutamine utilization by rat thymocytes was 8-fold increased during proliferation. The major end products of glutamine metabolism are glutamate, aspartate, CO2 and ammonia. A complete recovery of glutamine carbon and nitrogen in the products was obtained. The amount of glutamate formed by phosphate-dependent glutaminase which entered the citric acid cycle was enhanced 5-fold in the proliferating cells: 76% was converted into 2-oxoglutarate by aspartate aminotransferase, present in high activity, and the remaining 24% by glutamate dehydrogenase. With resting cells the same percentages were obtained (75 and 25). Maximal activities of glutaminase, glutamate dehydrogenase and aspartate aminotransferase were increased 3-, 12- and 6-fold respectively in proliferating cells; 32% of the glutamate metabolized in the citric acid cycle was recovered in CO2 and 61% in aspartate. In resting cells this proportion was 41% and 59% and in mitogen-stimulated cells 39% and 65% respectively. Addition of glucose (4 mM) or malate (2 mM) strongly decreased the rates of glutamine utilization and glutamate conversion into 2-oxoglutarate by proliferating thymocytes and also affected the pathways of further glutamate metabolism. Addition of 2 mM-pyruvate did not alter the rate of glutamine utilization by proliferating thymocytes, but decreased the rate of metabolism beyond the stage of glutamate significantly. Formation of acetyl-CoA in the presence of pyruvate might explain the relatively enhanced oxidation of glutamate to CO2 (56%) by proliferating thymocytes.
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PMID:Glutamine and glucose metabolism during thymocyte proliferation. Pathways of glutamine and glutamate metabolism. 286 9

Based on the selective inhibition of glutamate release in cerebellar granule cells in primary cultures by the aspartate aminotransferase inhibitor, aminooxyacetic acid, and by the ketodicarboxylate carrier inhibitor, phenylsuccinate, a novel model for synthesis of transmitter glutamate is suggested: Glutamate is formed from glutamine in the mitochondrial intramembrane space by phosphate-activated glutaminase, transported across the inner membrane in exchange with aspartate, transaminated in the matrix to alpha-ketoglutarate, which via the ketodicarboxylate carrier is transferred to the cytoplasm, and transaminated to form transmitter glutamate. Such a mechanism would explain the functional role of aspartate aminotransferase in glutamatergic neurons.
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PMID:Evidence that aspartate aminotransferase activity and ketodicarboxylate carrier function are essential for biosynthesis of transmitter glutamate. 289 6

Evidence is provided for the utilization of glutamine by calvaria and compact bone of rat. Glutamine was actively transported into calvaria, principally by sodium-dependent mechanisms; its uptake was significantly inhibited by neutral amino acids (alanine, proline, serine, asparagine) and glutamine analogs (L-glutamate-gamma-hydroxamate, albizziin). Glutamine was degraded to ammonia and glutamate by phosphate-dependent glutaminase, a mitochondrial enzyme present in both calvaria and compact bone. The enzyme exhibited an apparent Kmgln of 2.35 mM, a KactPO4 of 25 mM, and a broad pH optimum (7.5-9.5). It was inactivated by incubation of intact calvaria or bone homogenates with the glutamine analogs 6-diazo-5-oxo-L-norleucine (DON) and a 2-amino-4-oxo-5-chloropentanoic acid (chloroketone). Such treatment also severely inhibited (greater than 95%) both ammonia and 14CO2 formation from [U-14C]glutamine. Glutamate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase activities were measured in bone. Amino-oxyacetate, an aminotransferase inhibitor, inhibited 14CO2 formation from [U-14C]glutamine. The data indicate that glutamine can serve as a precursor of ammonia, glutamate, other amino acids (alanine, aspartate, ornithine, proline) and carbon dioxide in bone and that phosphate-dependent glutaminase, transaminases, and citric acid cycle activity contribute to the observed metabolism.
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PMID:Glutamine metabolism in bone. 613 80

The role of protein kinase C (PKC) in N-methyl-D-aspartate (NMDA) receptor-mediated biochemical differentiation and c-fos protein expression was investigated in cultured cerebellar granule neurons. The biochemical differentiation of glutamatergic granule cells was studied in terms of the specific activity of phosphate-activated glutaminase, an enzyme treatment in the synthesis of the putative neurotransmitter pool of glutamate. When the partially depolarized cells were treated with NMDA for the last 1 to 3 days (between 2 and 5 days in vitro), it elevated the specific activity of glutaminase. In contrast, NMDA had little effect on the activity of aspartate aminotransferase or of lactate dehydrogenase. Treatment of 10-day old granule neurons with NMDA also resulted in a marked increase in the immunocytochemically measured expression of c-fos protein. The increases in both the activity of glutaminase and the steady state level of c-fos protein were specific to the activation of NMDA receptors, as they were completely blocked by D,L-2-amino-5-phosphonovaleric acid. The specific stimulation of NMDA receptors in PKC-depleted granule neurons or in the presence of reasonably specific PKC inhibitors also produced significant elevation in the activity of glutaminase and the expression of c-fos protein. These increases were similar in magnitude to those observed in the granule neurons of the respective control groups. Our findings demonstrate that PKC is not directly involved in the NMDA receptor-mediated signal transduction processes associated with biochemical differentiation and c-fos induction in cerebellar granule neurons.
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PMID:Effects of protein kinase C modulation on NMDA receptor mediated regulation of neurotransmitter enzyme and c-fos protein in cultured neurons. 764 61

Glutamine is actively metabolized in human platelets, representing a preferential mitochondrial oxidative substrate in these cells. The primary importance of this metabolic route of glutamine is further confirmed here by the observation that platelet glutaminase activity is entirely represented by the phosphate dependent glutaminase or glutaminase I, most probably localized in the mitochondrial platelet fraction and classified by kinetic analysis as a kidney-type form. The following step of the glutamine metabolizing pathway, allowing the entrance of the amino acid skeleton carbons in the Krebs cycle, might be catalyzed by both glutamate dehydrogenase and aspartate transaminase, the first being entirely mitochondrial and the latter 65% mitochondrial. We also investigated platelets for the presence of one or more specific transport systems involved in glutamine uptake and we present the first evidence for two glutamine transport systems in human platelets that by inhibition analysis appear to share characteristics with the Na(+)-dependent ASC system and the Na(+)-independent L system for dipolar amino acid uptake. Both systems display affinity characteristics for glutamine in the range of plasma glutamine concentration and may thus have physiological relevance for the uptake of the amino acid in these cells.
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PMID:Glutamine transport and enzymatic activities involved in glutaminolysis in human platelets. 782 6


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