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:2.6.1.1 (aspartate aminotransferase)
21,665 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cysteine-glutamate transaminase (cysteine aminotransferase; EC 2.6.1.3) has been purified 149-fold to an apparent homogeneity giving a specific activity of 2.09 IU per milligram of protein with an overall yield of 15%. The isolation procedures involve the preliminary separation of a crude rat liver homogenate which was submitted sequentially to ammonium sulfate fractionation, TEAE-cellulose column chromatography, ultrafiltration, and isoelectrofocusing. The final product was homogenous when examined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS). A minimal molecular weight of 83 500 was determined by Sephadex gel chromatography. The molecular weight as estimated by polyacrylamide gel electrophoresis in the presence of SDS was 84 000. The purified enzyme exhibited a pH optimum at 8.2 with cysteine and alpha-ketoglutarate as substrates. The enzyme is inactivated slowly when kept frozen and is completely inactivated if left at room temperature for 1 h. The enzyme does not catalyze the transamination of alpha-methyl-DL-cysteine, which, when present to a final concentration of 10 mM, exhibits a 23.2% inhibition of transamination of 30 mM of cysteine. The mechanism apparently resembles that of aspartate-glutamate transaminase (EC 2.6.1.1) in which the presence of a labile hydrogen on the alpha-carbon in the substrate is one of the strict requirements.
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PMID:Purification and partial characterization of cysteine-glutamate transaminase from rat liver. 2 Feb 9

Acute 15, 30 and 60-minute hypoxia induced in a rabbit placed in the altitude chamber at the atmospheric pressure of 260 mm Hg was an experimental model for a hypoxic state. An increase in the amount of aspartate in the brain under conditions of 15-minute hypoxia and its decrease with prolongation of the hypoxia period up to 1 h may be explained by different mechanisms of amino acids metabolic transformations under these conditions. Changes in the content of aspartate are adequate to these in the activity of aspartate aminotransferase. An increase in the glutamate content in the brain the 30- and 60-minute hypoxic effect is accompanied by a rise of the activity in the glutamine synthesis enzyme (glutamine synthetase). Dynamics of the aspartate quantitative changes in the brain in different periods of acute oxygen deficiency affecting metabolic shifts in amino acids metabolism may serve as an index of the hypoxic effect gravity.
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PMID:[Peculiarities of amino acids transformation in brain under conditions of acute hypoxic hypoxia]. 3 21

Biotin deficiency in Aspergillus nidulans resulted in a 70% increase of the protein content and increased levels of free and bound aspartate, glutamate, serine, leucine and methionine. Likewise, the activities of NADP+ glutamate dehydrogenase, NAD+ gluatmate dehydrogenase, aspartate aminotransferase and alanine aminotransferase were significantly increased. The total RNA content increased while the DNA content was unaffected. The rRNA/tRNA ratio remained higher in biotin-deficient cells. Supplementation of glutamate, aspartate, serine, leucine and methionine to the culture medium raised the rRNA/tRNA ratio, and the difference observed in the qualitative and the quantitative patterns of protein and dry cell mass between normal and biotin-deficient cultures was abolished.
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PMID:Factors affecting protein synthesis during biotin deficiency in Aspergillus nidulans. 4 77

Differentiation and calcification of cartilage of a fracture callus morphologically, ultrastructurally, and histochemically resembles cartilage of growing epiphyseal plate. The fracture callus includes the various cartilage cell types found in the epiphyseal plate. Proliferating and hypertrophic cartilage had higher activities of cytochrome oxidase, alkaline phosphatase and glutamate aspartate transaminase than fibrocartilage. Enzymes controlling glycogen synthesis and glycolysis had higher levels of activity in fibrocartilage than in hypertrophic cartilage. Lysosomal enzymes, catalase, 6-phospho-gluconic acid and glucose 6-phosphate dehydrogenase were uniformly distributed. Alkaline phosphatase was associated with extracellular vesicles found in hypertrophic cartilage. EM dense granules were found in mitochondria in hypertrophic cartilage. There was an increase of total lipids in hypertropic and calcified cartilage as compared to resting cartilage.
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PMID:Morphological and biochemical studies during differentiation and calcification of fracture callus cartilage. 4 43

Adaptation of Ehrlich ascites tumor cells to serial cultivation in media with progressively elevated (hypertonic) NaCl content ("high NaCl"-tolerant cells) has resulted in progressive increases of the cellular activities of NAD-dependent glycerol-3-phosphate dehydrogenase (EC 1.1.1.8), NAD-dependent malate dehydrogenase (EC 1.1.1.37), glutamate--oxalacetate transaminase (EC 2.6.1.1), NAD (P)-dependent glutamate dehydrogenase (EC 1.4.1.3), NADP-dependent isocitrate dehydrogenase (EC 1.1.1.42). The activities of glutamate-pyruvate transaminase (EC 2.6.1.2.) and of glycolytic enzymes as phospho-fructokinase (EC 2.7.1.11), glyceraldehydephosphate dehydrogenase (EC 1.2.1.12) and lactate dehydrogenase (EC 1.1.1.27) were only slightly and not in progressive manner (in response to the progressive increase of the environmental NaCl concentration) affected. These changes are discussed with respect to a metabolic pattern of these "high NaCl"-tolerant cells which is compatible with increased energy requirements, especially for active cation transport. It is suggested that these increased cellular enzyme activities reflect an increased transfer of reducing equivalents across mitochondrial membranes (via the "glycerophosphate cycle and the malate-aspartate shuttle") and possibly a stimulated lipid metabolism. These alterations in the level of enzyme activities must be regarded asan adaptive cellular response to the "high NaCl" environment, since readaptation to growth in regular isotonic media resulted in a reversion to the enzyme pattern characteristic of the parent cells.
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PMID:Changes in enzyme pattern of Ehrlich ascites tumor cells following serial cultivation in media with increased (hypertonic) NaCl content. 12 1

Mitochondrial aspartate aminotransferase, an enzyme localized on the inner face of the inner mitochondrial membrane, is released into the intermembrane space upon addition of a "movement effector" (succinate, fumarate, pyruvate, or glutamate) [Waksman, A., & Rendon, A. (1974) Biochimie 56, 907-924]. After removal of the movement effector, 90% of the released enzyme rebound to mitoplasts. Lubrol fractionation showed that this bound activity was associated with the inner membrane. Internalization was demonstrated by using both enzymatic and molecular approaches. It was found that 70% of the reassociated enzyme became inaccessible from the outside of the mitoplast either to a nonpermeating substrate (NADH), to mild protease hydrolysis, or to recognition by a specific antibody. In contrast, in inside-out vesicles, the enzyme remained accessible to NADH, protease, and antibodies. Latency measurements performed at different temperatures on whole intact mitochondria confirmed the existence of reversible intermembrane movement of the enzyme in situ.
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PMID:Direct evidence for internalization of mitochondrial aspartate aminotransferase into mitoplasts. 22 27

A method for the purification of two cysteinesulphinate transaminases, A and B (EC 2.6.1), is described. These enzymes catalyse the conversion of cysteinesulphinic acid to beta-sulphinyl pyruvate. The final preparations are homogeneous by polyacrylamide gel electrophoresis, sodium dodecyl sulphate-polyacrylamide gel electrophoresis and isoelectrofocusing. The molecular weight of the subunits is 41 000 for cysteinesulphinate transaminase A and 43 400 for B. Both enzymes are unspecific, as L-asparate, L-glutamate and L-cysteic acid serve as substrates in addition to L-cysteinesulphinic acid. Cysteinesulphinate transaminase A has a Km of 9.8 mM for cysteinesulphinic acid and 0.25 mM for aspartic acid, whereas the B enzyme has a Km of 6.5 mM for cysteinesulphinic acid and 1.4 mM for aspartic acid. The Vmax values of the A and B enzymes are respectively 7.1 and 6.2 mmol h-1 mg-1 protein for aspartic acid and 45 and 9.3 mmol h-1 mg-1 protein for cysteinesulphinic acid. Both enzymes exhibit maximum activity at pH 8.6. A high specific activity is found in optimal conditions for these two transaminases, the pI values being 9.06 and 5.70 for cysteinesulphinate transaminase A and B respectively. These results have been compared with those already obtained for purified aspartate aminotransferase. Similarities in the pathways of taurine and gamma-aminobutyric acid (GABA) metabolism are discussed.
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PMID:Similarities between cysteinesulphinate transaminase and aspartate aminotransferase. 26 60

Catalysis-linked conformational transitions of aspartate aminotransferase (cytosolic isoenzyme from pig heart; L-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1) have been probed by infrared spectrophotometric measurement of hydrogen-deuterium exchange. In the unliganded pyridoxal form of the enzyme at pH 6.0 and 20 degrees, 43% of the total 411 peptide hydrogens per subunit exchange within the first 10 min. An additional 9% exchange slowly in the following time period to 360 min. A quite similar exchange curve is obtained with the pyridoxamine form of the enzyme, indicating close correspondence in conformation of both unliganded forms of the enzyme. Formation of a nonproductive adsorption complex of the pyridoxal enzyme with 2-oxoglutarate or of the pyridoxamine enzyme with glutamate alters the exchange characteristics only slightly. In contrast, the formation of an equilibrium mixture of the covalent transamination intermediates, which occurs in the silultaneous presence of the amino acid and the keto acid substrate, results in a marked retardation of hydrogen exchange, reflecting a substantial tightening of the structure of the enzyme. The exchange reactions of at least 26 peptide hydrogens per subunit (6% of the total) are retarded by a factor of 6 on the average. The occurrence of such syncatalytic conformational changes reflects energetic coupling of the covalency changes at the active site with conformational changes of the macromolecular protein matrix that may contribute to optimizing the free energy profile of enzymic transamination.
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PMID:Syncatalytic conformational changes in aspartate aminotransferase determined by hydrogen-deuterium exchange. 27 28

The effects of glutamine deprivation on cultured skeletal muscle cells were analyzed by incubating 10-day-old myotube preparations in glutamine free Dulbecco's modified Eagle medium containing 10% fetal calf serum for up to 48 h. Under these conditions net glutamine production was not observed, but active ammonia production (average rate = 1.0 nmol/min . mg protein) continued despite glutamine withdrawal. Glutamine deprivation was associated with a progressive depletion of intracellular aspartate and glutamate. Maximal aspartate depletion correlated with a 15-fold increase in the intracellular lactate:pyruvate ratio and a 3-fold decrease in the estimated intracellular glutamate:(alpha-ketoglutarate) (ammonia) ratio. Despite wide shifts in cell metabolite concentrations, the mass action ratios of alanine and aspartate aminotransferase approximated the expected equilibria constants. These results suggest that 1) glutamine deprivation is associated with a marked reduction of aspartate, and the maintenance of aspartate depletion is due in part to the tendency of aspartate aminotransferase to maintain the metabolites of this reaction at a near equilibrium level; 2) the transport of reducing equivalents from the cytosolic to the mitochondrial compartments via the malate-aspartate shuttle may be limited under conditions of aspartate depletion.
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PMID:Effects of glutamine deprivation on glucose and amino acid metabolism in tissue culture. 42 54

The mitochondrial matrix subfractions from rat liver, kidney cortex, brain, heart, and skeletal muscle were isolated and their protein components were resolved by two-dimensional polyacrylamide gel electrophoresis, revealing between 120 and 150 components for each matrix subfraction. Excellent resolution was obtained utilizing a pH 5 to 8 gradient in the first dimension and in 8 to 13% exponential acrylamide gradient in the second dimension, increasing the number of mitochondrial matrix proteins observed 3-fold over one-dimensional systems. Protein components tentatively identified by co-migration with pure enzymes and by known tissue distributions are carbamoyl-phosphate synthetase (EC 2.7.2.5), ornithine transcarbamylase (EC 2.1.3.3), glutamate dehydrogenase (EC 1.4.1.3), pyruvate carboxylase (EC 6.4.1.1), citrate synthase (EC 4.1.3.7), fumarase (EC 4.2.1.2), aconitase (EC 4.2.1.3), alpha-ketoglutarate dehydrogenase (EC 1.2.4.2), dihydrolipoyl transsuccinylase (EC 2.3.1.12), lipoamide dehydrogenase (EC 1.6.4.3), glutamate-aspartate aminotransferase (EC 2.6.1.1), and the two subunits of pyruvate dehydrogenase (EC 1.2.4.1). Protein components unambiguously identified by peptide mapping are citrate synthase, aconitase, and pyruvate carboxylase. The inner membrane subfraction from rat liver mitochondria was also resolved two dimensionally; the alpha and beta subunits of ATPase (F1) (EC 3.6.1.3) were identified by peptide mapping.
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PMID:Resolution of rat mitochondrial matrix proteins by two-dimensional polyacrylamide gel electrophoresis. 44 63


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