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)

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

Aspartate aminotransferase in the sera of normal subjects and of patients with hepatic diseases has been immunologically separated into two isoenzymes, cytosolic aspartate aminotransferase and mitochondrial aspartate aminotransferase. The activity of the isoenzymes was measured in three different buffer solutions with or without pyridoxal 5'-phosphate. To attain maximal activation, the apoenzyme of mitochondrial fraction must be preincubated with pyridoxal 5'-phosphate longer than that of the cytosolic fraction in either of the three reaction mixtures. In most sera the activity of both isoenzymes increased substantially in the presence of pyridoxal 5'-phosphate regardless of the type of buffer solutions. Both the apoenzymatic activity and the ratio of apo- to holo-enzymatic activity of each of the isoenzymes varied among samples from the patients with hepatic diseases. However, significantly high ratios of apo- to holo-enzymatic activity of both isoenzymes were observed in the patients with hepatoma in contrast with those with other hepatic diseases. These findings suggest that the simultaneous measurement of both apo- and holo-enzyme activities of aspartate aminotransferase isoenzymes may be useful in the clinical assessment of hepatic diseases.
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PMID:Apoenzyme of aspartate aminotransferase isozymes in serum and its diagnostic usefullness for hepatic diseases. 22 64

FUSE, a human gene which promotes polykaryocyte formation, has been identified and examined in cocultivation assays between rat XC cells and human-mouse hybrids retaining different combinations of human chromosomes. Polykaryocyte formation was never detected when parental cells of hybrids were cocultivated with XC cells. Somatic genetic synteny analysis employing different hybrid sets demonstrated that FUSE was coexpressed with the chromosome 10 markers glutamate oxaloacetate transaminase (GOTs) and an external membrane protein (EMP-130). Cytogenetic analysis confirmed this assignment to human chromosome 10. FUSE was expressed by hybrids made with both human leukocytes and fibroblasts from several individuals, indicating the gene is found in different tissues and may be ubiquitous. Only XC cells were involved in polykaryocyte formation as demonstrated by 33258 Hoechst staining and the absence of heteropolymers between rat and cell hybrid multimeric enzymes. Evidence suggests that the gene FUSE produces a nondiffusible and noninfectious product that is associated with the human-mouse hybrid surface.
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PMID:Genetics of cell fusion: human chromosome 10 assignment of a gene (FUSE) that promotes polykaryocyte formation. 22 23

The effect of N6,O2'-dibutyryl adenosine 3',5'-cyclic-monophosphate (dbcAMP) on the mobilization of calcium (Ca2+), inorganic phosphate (Pi) and lysosomal enzymes was studied in a bone culture system for 24 h using half calvaria from 6--7 day-old mice. DbcAMP inhibited spontaneous as well as parathyroid hormone-stimulated mineral mobilization. DbcAMP in a concentration of 5 x 10(-4)M also reduced the activities of beta-glucuronidase, beta-galactosidase and acid phosphatase found in the media while the activities of lactate dehydrogenase, aspartate aminotransferase and alanine aminotransferase were not affected. It is concluded that cAMP is not a stimulator but an inhibitor of bone resorption within the culture period studied (24 h) and that the cyclic nucleotide might interfere with release processes involved in bone resorption.
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PMID:Inhibitory effect of dibutyryl cyclic AMP on the release of calcium, inorganic phosphate and lysosomal enzymes from calvarial bones cultured for 24 hours. 22 6

The levels of tyrosine, aspartate and alanine aminotransferases of fetal rat liver were measured and compared with values reported in the literature. Incubation of explants of fetal liver in organ culture resulted in spontaneous increases in tyrosine and alanine aminotransferases, and decrease in aspartate aminotransferase.
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PMID:Activities of tyrosine, alanine and aspartate aminotransferases of fetal rat liver in organ culture. 23 79

Two aminotransferases from Escherichia coli were purified to homogeneity by the criterion of gel electrophoresis. The first (enzyme A) is active on L-aspartic acid, L-tyrosine, L-phenylalanine, and L-tryptophan; the second (enzyme B) is active on the aromatic amiono acids. Enzyme A is identical in substrate specificity with transaminase A and is mainly an aspartate aminotransferase; enzyme B has never been described before and is an aromatic amino acid aminotransferase. The two enzymes are different in the Vmax and Km values with their common substrates and pyridoxal phosphate, in heat stability (enzyme A being heat-stable and enzyme B being heat-labile at 55 degrees) and in pH optima with the amino acid substrates. They are similar in their amino acid composition, each enzyme appears to consist of two subunits, and enzyme B may be converted to enzyme A by controlled proteolysis with subtilsin. The conversion was detected by the generation of new aspartate aminotransferase activity from enzyme B and was further verified by identification by acrylamide gel electrophoresis of the newly formed enzyme A. The two enzymes appear to be products of two genes different in a small, probably terminal, nucleotide sequence.
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PMID:Multispecific aspartate and aromatic amino acid aminotransferases in Escherichia coli. 23 11

With respect to the enzymes of NADPH-forming metabolic pathways in human leukocytes: (a) Glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase (decarboxylating) were less active in leukocytes (mostly myeloblasts) from eight patients with acute myeloblastic leukemia (I) than in leukocytes (mostly granulocytes) from 16 normal subjects (II). (b) Of the enzymes of the citrate cleavage pathway, ATP citrate lyase and malate dehydrogenase (decarboxylating) (NADP+) were virtually absent in the cells studied. (c) Isocitrate dehydrogenase (NADP+), aspartate aminotransferase, and alanine aminotransferase, which, together with the much more active malate dehydrogenase, constitute a newly proposed NADPH-forming metabolic cycle, showed a higher activity in I than in II or III, and therefore could compensate, as concerns NADPH-generation, for the low activity of pentose cycle dehydrogenases. We are not sure whether the enzymatic characteristic of I cells is attributable to their immaturity or to their leukemic nature.
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PMID:Enzyme activities of NADPH-forming metabolic pathways in normal and leukemic leukocytes. 23 46

The interactions were studied of the apoenzyme of aspartate aminotransferase from chicken heart cytosol with a variety of pyridoxal-P analogues. 2-Norpyridoxal-P, 2'-n-propylpyridoxal-P, 2'-isopropylpyridoxal-P, 6-methylpyridoxal-P, and 5'-methylpyridoxal-P were shown to display coenzyme activity. Estimated relative Vmax values of the complexes of apoenzyme with the above--mentioned analogues amounted respectively to 0.8; 0,2; 0,1; 0.1 and 0.1 (taking the Vmax value of the native holoenzyme as equal 1.0). The pH-dependence of reactivation rates of the apoenzyme with pyridoxal-P and pyridoxamine-P was evaluated. 3-Deoxypyridoxal-P, 3-0-methylpyridoxal-P, 2'-phenylpyridoxal-P, 5-nor-5-beta-carboxyvinylpyridoxal and 5-nor-5-beta-carboxyethylpyridoxal fail to activate the apoenzyme, but inhibit competitively the binding of pyridoxal-P to the protein; the estimated Ki values for these analoges were 2.4-10- minus 6; 3.1-10- minus 6; 3.5-10- minus 6; 7.2-10- minus 6 and 8.3-10- minus 6 M, respectively. It is of interest to compare reactivation effects of pyridoxal-P analogues for the apoenzymes of aspartate aminotransferases from chicken and from pig heart cytosol. Although the observed effects were fairly similar, it should be noted that the relative catalytic efficiencies of complexes of the chicken apoenzyme with pyridoxal-P analogues were much lower than those of complexes formed with the pig heart apoenzyme. It thus appears that of the two enzymes tested, the chicken heart aminotransferase makes more stringent demands with respect to structure of the coenzyme.
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PMID:[Interaction of aspartate transaminase from chicken heart cytosol with pyridoxal phosphate analogs]. 23 82

DL-alpha-Methyltryptophan (alphaMeTrp), a synthetic analogue of tryptophan, has been found to be a potent inducer of hepatic tyrosine aminotransferase activity in the adrenalectomized rat. alphaMeTrp is inactive in vitro. Unlike the action of other known inducers (tryptophan, hydrocortisone, adenosine cyclic 3:5-monophosphate, and glucagon), maximal stimulation of enzyme activity occurs only 16 to 30 hours after alphaMeTrp administration and the activity is still elevated at 96 hours. Only the L isomer of alphaMeTrp is active, and addition of a hydroxyl group to position 5 of the indole ring renders an inactive compound. The induction can be prevented by actinomycin D or cycloheximide but not galactosamine. Administration of alphaMeTrp together with hydrocortisone produced an additive stimulation of enzyme activity. alphaMeTrp given along with glucagon or adenosine cyclic 3:5-monophosphate caused a further but not additive increase in enzyme activity. Tryptophan given along with alphaMeTrp promoted no extra stimulation whatsoever. These data indicate that alphaMeTrp and tryptophan may act via a common pathway which in part requires RNA synthesis. Other enzymes, namely alanine and aspartate aminotransferase, ornithine aminotransferase, ornithine carbamoyltransferase, serine dehydratase, and histidine ammonialyase, were not affected by treatment of rats with alphaMeTrp.
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PMID:Stimulation of tyrosine aminotransferase activity by dl-alpha-methyltryptophan. 23 76

Serum gamma glutamyl transpeptidase (GGTP), isocitrate dehydrogenase (ICD), ornithine carbamoyl transferase (OCT), alanine aminotransferase (AlT), aspartate aminotransferase (AsT), and alkaline phosphatase (ALP) activities were assayed in 67 alcoholics and 40 drug dependent patients. Bilirubin, total protein, albumin, and globulin were also measured. GGTP elevation was observed in 48% of alcoholics and in 50% of drug dependents. The incidences of elevated levels of other enzymes were: ICD 39 and 38-7%; OCT 23-7 and 36-1%; AlT 30 and 33%; AsT 24-2 and 21-7%; ALP 10-4 and 5% respectively. Measurement of GGTP is thus more useful as a screening test for involvement of the liver in alcoholics and drug dependent patients than that of the other enzymes.
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PMID:Serum enzyme levels in alcoholism and drug dependency. 23 23


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