Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.6.1.2 (alanine aminotransferase)
 26,722 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Most of the hybrid clones derived from a cross of Chinese hamster fibroblasts (DON) with rat hepatoma cells (Faza 967) showed preferential loss of rat chromosomes. Two of the hybrid clones retained the rat chromosomes, and both showed extinction of 4 liver-specific enzymes: aldolase B, liver alcohol dehydrogenase, and the inducible enzymes tyrosine aminotransferase and alanine aminotransferase. Subcloning of 1 of these hybrids, which contained 2 sets of hepatoma chromosomes and 1 set of hamster chromosomes, permitted the isolation of some clones which reexpressed 1 or more of the liver-specific enzymes. Liver alcohol dehydrogenase was the most frequently reexpressed enzyme and aldolase B the least. Tyrosine aminotransferase inducibility was reexpressed independently of basal activity, and the enzyme produced by the reexpressing hybrid cells was precipitated by a specific antiserum. No correlation was detected between the presence or absence of the marker chromosomes (large metacentrics) of the hamster parent and the extinction and reexpression of the hepatic enzymes. The results reported confirm and extend to interspecific hybrids the observation of the stable and independent reexpression of tissue-specific enzymes.
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PMID:Expression of differentiated functions in hepatoma cell hybrids: IX extinction and reexpression of liver-specific enzymes in rat hepatoma-Chinese hamster fibroblast hybrids. 1 64

A cross has been performed between dedifferentiated rat hepatoma cells and the differentiated cells from which they were derived. 10 hybrid clones, containing the complete chromosome sets of both parents, show extinction of 4 liver-specific enzymes: tyrosine aminotransferase (E.C. 2.6.1.5), alanine aminotransferase (E.C. 2.6.1.2), and the liver-specific isozymes of alcohol dehydrogenase (E.C. 1.1.1.1) and aldolase (E.C. 4.1.2.13). Moreover, the 4 hybrid clones examined do not produce albumin . The only function of the differentiated parent which is not extinguished in the hybrid cells is inducibility of the aminotransferases. For 3 of the hybrid clones, extinction of 3 of the 4 enzymes is incomplete, but these clones do not differ in modal chromosome number from those which show more complete extinction of the enzymes. Subcloning of several of the hybrids revealed that the phenotype of the hybrids is very stable; 4 subclones showing reexpression of intermediate levels of the enzymes are characterized. These results show that dedifferentiation of the parental cells is not due to the simple loss of some factor required for the maintenance of expression of differentiated functions, and suggest that dedifferentiation is due to the activation of some control mechanism, whose final effect is negative, and which may be a part of the epigenotype of the embryonic hepatocyte.
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PMID:Extinction of liver-specific functions in hybrids between differentiated and dedifferentiated rat hepatoma cells. 1 65

Comparative biochemical studies on phosphorylase b, aspartate aminotransferase and alanine aminotransferase in muscles of various vertebrates (the lamprey Lampetra fluviatilis, dogfish Squalus acanthias, rays Dasyatis pastinaca and Raja clavata, teleosts Scorpaena porcus, Spicara smaris, Esox lucius, Tinca tinca, Abramis brama, Lucioperca lucioperca, Cyprinus carpio, Salmo ischchan, frog Rana temporaria, tortoise Testudo horsfieldi) revealed some peculiarties of their molecular evolution. It was shown that isoenzyme PH-II, which comprises in most on the investigated lower vertebrates the main bulk of phosphorylase b, disappears in evolution of the type. Isoenzyme PH-I which is found in fisches in small amounts, increases in evolution becoming the sole form of phosphorylase b in skeletal muscles of endothermic animals. Mitochondrial and cytoplasmic isoenzymes of aspartate aminotransferase were found in all the vertebrates studied. Cytoplasmic isoenzyme from ectothermic and endothermic animals does not differ significantly, whereas the mitochondrial one undergoes considerable changes in the evolution of vertebrates.
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PMID:[Molecular evolution of glycogen phosphorylase and aminotransferases of vertebrate muscle tissue]. 1 51

The role of coenzyme in determining intracellular contnet of pyridoxal enzymes was assessed by analyzing effects of pyridoxine deficiency on the rapidly degraded, readily dissociable tyrosine aminotransferase (EC 2.6.1.5) and the slowly degraded, nondissociable alanine aminotransferase (EC 2.6.1.2) of rat liver. Synthesis of the tyrosine enzyme was reduced, leading to a decreased amount of this enzyme, much of which was present as active apoenzyme. Synthesis of alanine aminotransferase was unchanged but much of this enzyme was present as an inactive apoenzyme which retained immunological reactivity. Degradation rates of both enzymes (t1/2 about 1.5 h, tyrosine aminotransferase; about 3 days, alanine aminotransferase) were not changed in pyridoxine deficiency. Hence, interaction with coenzyme is not a significant determinant in intracellular degradation of these aminotransferases. Coenzymes dissociation and intracellular stability probably reflect structural features of the proteins which determine both properties.
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PMID:Role of coenzyme in aminotransferase turnover. 1 9

The activities of GOT, GPT, LDH, gamma-glutamyltranspeptidase (gamma-GTP), alkaline phosphatase (AP), glutamate dehydrogenase (GLDH) and the concentrations of bilirubin in blood plasma after a single intraruminal application of aflatoxins were studied in four dairy cows. The maximum changes in the activities of the enzymes and the maximum bilirubin concentration in plasma were obtained in the first two to three days following the application of aflatoxins. The statistically significant increase of GOT activity, compared with activity before the application of aflatoxins, persisted until the 23rd day; in the case of LDH and GLDH the increase persisted until the 38th day from the application of aflatoxins. The activities of gamma-GTP and AP were slightly higher even on the 50th day. The increased concentration of bilirubin in plasma lasted until the 23rd day from aflatoxin application. The increased activities of enzymes testify to an impaired function of the liver, which is also proved by the specific enzymes GLDH, gamma-GTP, by increased bilirubin levels, and by histological changes known from literature. The evaluation of enzymatic activities and bilirubin concentration in plasma can make a valuable contribution to correct diagnosis of aflatoxicoses in cattle.
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PMID:[Changes in enzyme activity induced by experimental aflatoxicosis in dairy cows]. 1 36

Details of a systematic approach to suitability testing of commercial control sera are given for substrate optimized L-aspartate aminotransferase and L-alanine aminotransferase methods at 37 degrees C. Their acceptability for control purposes of standardized methods depends on: (1) the range of control values in relation to borderline values, (2) stability, (3) aspect, clarity, (4) NADH consumption in preincubation time, (5) blank activities, (6) kinetic data as half saturation constants and saturation curves, (7) influence of effectors, (8) isoenzyme pattern. These evaluation criteria are proposed for suitability testing. The term "representativeness" should be introduced as a special criterion for main characteristics of control materials. The authors want to point out the close connection with standardization of methods.
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PMID:Suitability of commercial enzyme control sera for the quality control of activity determinations of L-aspartate aminotransferase and L-alanine aminotransferase in human serum. 1 83

In an earlier report from this laboratory, one of the early manifestations of hypervitaminosis A was shown to be a marked stimulation of hepatic gluconeogenesis. In the present study, effects of feeding 30,000 IU of retinyl palmitate to young rats (80-100 g), once daily, for 2 days on the incorporation of 14C-labeled precursors into glucose and glycogen by liver slices, levels of amino acids in blood and tissues, and activities of some important amino acid catabolizing enzymes in the liver were investigated. A stimulation of hepatic gluconeogenesis in hypervitaminosis A was indicated by the increased incorporation of 14C-labeled alanine and bicarbonate into glucose and glycogen by liver slices. Excessive intake of retinol caused a marked increase in the activities of hepatic alanine aminotransferase and ornithine aminotransferase and a decrease in that of tryptophan pyrrolase, without affecting those of tyrosine aminotransferase and serine dehydratase. The ratio of NADH:NAD in the livers of rats fed excess retinol was significantly increased. It is suggested that enhancement of glucoeogenesis in hypervitaminosis A is caused by a stimulation of gluconeogenic activity of the liver.
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PMID:Early effects of hypervitaminosis A on gluconeogenic activity and amino acid metabolizing enzymes of rat liver. 2 Apr 86

Conditions for accurate measurement of catalytic activity of aspartate aminotransferase and alanine aminotransferase in human serum have been reinvestigated. The basic variables (kind of buffer, buffer concentration, pH, ion effects, and the influence of pyridoxal-5-phosphate) can now be considered optimized. On this basis, the kinetic parameters of both aminotransferases were determined, i.e., Michaelis and inhibitor constants for substrates and reaction products. With a mathematical approach for two-substrate enzyme reactions the substrate concentrations were calculated from the viewpoints "most economical," "most convenient," and "lowest variability." Also the conditions for the indicator reactions have been newly defined with respect to a kinetic model. All calculated data were rechecked experimentally and it can be shown that both approaches fully agree. Furthermore, we show that the mathematical approach allows more precise recommendations for optimized methods. For technical reasons, the catalytic activity of aspartate aminotransferase in human serum can only be measured as a 0.96 fraction of its theoretical maximum velocity, the catalytic activity of alanine aminotransferase as a 0.91 fraction. The assay conditions for a Reference Method are finally described and recommendations are made for optimized routine methods for determination of the catalytic activity of these transferases in human serum.
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PMID:Optimization of methods for aspartate aminotransferase and alanine aminotransferase. 2 9

The recent hypothesis that phototherapy is capable of altering the liver cell, enough to allow passive diffusion of free bilirubin from the blood to the bile, and the discovery of substantial differences between the breakdown products of bilirubin obtained in vivo and in vitro, has prompted the AA. to investigate the enzymatic values in newborn infants with jaundice undergoing phototherapy. A study was made of the variations of cytolithic enzymes (GPT-GOT-GLDH-SDH) and secretions enzymes (FA-LAP-gammaGT-CHE) before and after phototherapy among different sized groups of infants with jaundice, between the 36th and 40th week of the gestational age, and with body weight varying from 1940 to 4150 g. No significant alteration of the cytolithic enzymes were recorded and among the secretion enzymes only the gammaGT was seen to increase. According to the AA., phototherapy does not alter the presence of a possible transitory cholestasis in newborn infants with physiological jaundice and causes no significant damage to the liver cells.
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PMID:[Behavior of some liver enzyme activities in newborn infants with jaundice treated with phototherapy]. 2 91

The lysosomal glycosidase N-Acetyl-beta-glucosaminidase (beta-NAG) is involved in the breakdown of connective tissue. The activity of this enzyme was determined in sera and biopsies of liver tissue from patients with chronic diseases of the liver of different aetiology. Elevation of enzyme activity was found to be related to an increase of the mesenchymeraction in the injured liver tissue. No correlation was found between activity of beta-NAG and of GPT, gammaGT and CHE.
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PMID:[Consideration of the mesenchyme-reaction in patients with cronical liver-diseases (author's transl)]. 2 15


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