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)

1. Changes in hepatic and renal glutathione (GSH) and plasma aspartate aminotransferase (AST) following single or daily oral doses of aflatoxin B1 (AFB1, 2 mg/kg BW) or corn oil vehicle (1 ml/kg BW) were determined in male chickens (14-21-day-old). 2. Plasma AST and hepatic GSH increased 2 and 8 hr, respectively, following a single AFB1 dose. 3. Hepatic GSH continued to increase through 5 daily doses of AFB1, but there were no differences in AST levels on days 1-5. Feeding a diet containing 150% of NRC requirement for methionine attenuated the AFB1-induced increase in hepatic GSH. Renal GSH was unaffected by AFB1 or dietary treatment.
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PMID:Aflatoxin and glutathione in domestic fowl (Gallus domesticus)--I. Glutathione elevation and attenuation by high dietary methionine. 135 97

In four abnormal fibrinogens with a point mutation in the gamma chain, all characterized by impaired fibrin polymerization, we identified single base exchanges in the respective mutant gamma chain genes by polymerase chain reaction followed by DNA sequence analysis. These base exchanges accounted for the amino acid substitutions previously reported from our laboratory. They were exchanges of C to T (CGC for gamma Arg-275 to TGC for Cys) in fibrinogen Osaka II, T to G (AAT for gamma Asn-308 to AAG for Lys) in fibrinogen Kyoto I, T to C (ATG for gamma Met-310 to ACG for Thr) in fibrinogen Asahi, and G to T (GAT for gamma Asp-330 to TAT for Tyr) in fibrinogen Kyoto III. These base exchanges were found to reside in exon VIII of the gamma chain gene. Since many abnormal molecules are associated with polymerization defects, unless associated with the impaired release of fibrinopeptides A and/or B, exon VIII of the gamma chain gene may deserve careful study to define the structural alterations.
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PMID:Gene analyses of abnormal fibrinogens with a mutation in the gamma chain. 142 Nov 74

The distribution of amino acids between plasma, liver and brain was studied in adult male rats, fed a diet containing 8.7, 17 (control animals), 32 and 51% of protein during 15 days. The caloric intake was nearly equal in all groups. The highest food intake was observed in the animals on the low protein diet. Changes in plasma amino acids were variable. In contrast to the behavior of most amino acids in plasma, the branched chain amino acids were highest in the animals fed the 51% protein diet. Despite the low protein intake in the animals fed a 8.7% protein diet, the concentration of serine, glutamic acid, glutamine, glycine, alanine, methionine, isoleucine, leucine, phenylalanine and ornithine were significantly higher compared to control animals, whereas in those receiving a high protein diet, valine, leucine, tyrosine, tryptophan and histidine increased in relation to the increased protein and amino acid intake. The plasma amino acid patterns are not greatly influenced by the amino acid distribution in the food and the amount ingested. Alanine aminotransferase, aspartate aminotransferase, glutamate dehydrogenase and cholinesterase showed a two- to fivefold increased activity in the liver of animals consuming a high protein diet. In the brain, the concentration of valine, leucine, isoleucine, phenylalanine and tyrosine in animals receiving the low protein diet was higher than in controls and increased further with increasing protein content of the diet. Glutamine was increased in all dietary groups. The predicted influx of amino acids showed increasing influx rates in dependence of the plasma amino acid concentration. The entry of tyrosine and tryptophan and their brain concentration was inversely proportional to the protein content of the diet. In the present study which considers long-term adaptation to an increasing protein and amino acid intake in comparison to a balanced control protein diet, the levels of the indispensable amino acids were maintained within narrow limits in the brain and liver. The results indicate that inspite of a variable protein intake, the body tends to keep organ amino acids in relatively narrow limits favoring in this way amino acid homeostasis.
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PMID:Effect of different protein diets on the distribution of amino acids in plasma, liver and brain in the rat. 159 Jun 69

The precise role of lipid peroxidation in the pathogenesis of alcoholic liver disease is still being debated. To explore the issue, this study was undertaken to investigate the status of lipid peroxidation, antioxidants and prooxidants at two discrete stages of experimental alcoholic liver disease. Male Wistar rats were intragastrically fed a high-fat diet plus ethanol for 5 or 16 wk (the duration that resulted in initiation of centrilobular liver necrosis or liver fibrosis, respectively). Lipid peroxidation was assessed in isolated microsomes and mitochondria with three parameters: malondialdehyde equivalents as determined by thiobarbituric acid assay, conjugated diene formation and 4-hydroxynonenal as a 2,4-dinitrophenylhydrazone derivative. To assess antioxidant systems, hepatic concentrations of glutathione, methionine and alpha-tocopherol were determined. The concentration of nonheme iron, a known prooxidant, was also measured. At wk 5, centrilobular liver necrosis was already evident in the ethanol-fed animals, with two- or threefold increases in plasma AST and ALT levels. At this stage, neither malondialdehyde equivalents nor conjugated diene values were elevated, and the 4-hydroxynonemal level was below 0.2 nmol/mg protein. Hepatic concentrations of methionine and alpha-tocopherol in these animals were increased two- and threefold, respectively, whereas the reduced glutathione level remained unchanged. When alcoholic liver disease had progressed to perivenular or bridging fibrosis at wk 16, all three parameters of lipid peroxidation showed consistent increases that were accompanied by significant reductions in the hepatic glutathione and methionine levels. Interestingly, the control animals pair-fed with the high-fat diet also had significantly elevated 4-hydroxynonenal levels at wk 16 compared to the wk 5 level.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Increased 4-hydroxynonenal levels in experimental alcoholic liver disease: association of lipid peroxidation with liver fibrogenesis. 163 54

A study was performed to determine whether dietary pyridoxine affects the response of rats to arsenic deprivation. A 2 x 2 x 2 factorially arranged experiment utilized groups of 6 male weanling Sprague-Dawley rats. They were fed a 14% amino acid/76% acid-washed corn diet for 10 weeks. The dietary variables were arsenic, 0 or 1 microgram/g; pyridoxine.HCl, 0 or 10 mg/kg, and L-methionine, 0 or 3 g/kg. The basal diet contained 0.24% methionine (calculated) and about 10 ng arsenic/g. Growth was reduced by arsenic, pyridoxine or methionine deprivation. Other parameters including blood indices, erythrocyte aspartate aminotransferase and the concentration of tissue iron and plasma amino acids were affected by dietary arsenic, pyridoxine, methionine or their interaction. The data demonstrate that dietary pyridoxine and arsenic interact and that the methionine status of the animal can affect this interaction.
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PMID:Effect of dietary pyridoxine on arsenic deprivation in rats. 166 17

A study was conducted to investigate morphologic as well as metabolic characteristics of microcarrier-attached hepatocytes in culture, and also to evaluate the effect of intraperitoneal transplantation of the microcarrier-attached hepatocytes on acute hepatic failure in rats induced by D-galactosamine (GalN). Rat hepatocytes were isolated by collagenase perfusion, and cultured on collagen-coated microcarriers. Protein synthesis estimated by [14C] leucine incorporation was four-fold higher in microcarrier culture than in cell suspension. The rates of albumin, transthyretin and bile acid syntheses in hepatocytes cultured on microcarriers were similar to those in monolayer culture. When microcarrier-attached hepatocytes were intraperitoneally transplanted into rats with Galn-induced acute liver failure, a marked improvement in survival rate was observed as compared with control rats which received injections of microcarriers alone (80% vs 0% beyond 6 days of transplantation). Mean serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), methionine and glucose levels were similar in both groups, while serum bilirubin and ammonia levels were lower (P less than 0.1, P less than 0.05) in rats transplanted with the microcarrier-attached hepatocytes. Immunohistochemical examinations revealed that the transplanted hepatocytes around microcarriers had albumin synthesis activity, whereas almost no albumin synthesis was demonstrated in recipient liver. In conclusion, intraperitoneal transplantation of the microcarrier-attached hepatocytes will provide sufficient metabolic support, representing detoxication of ammonia (and presumably bilirubin) and synthesis of albumin, to allow GalN-damaged liver function to restore. Microcarrier culture of isolated hepatocytes seems to be one of the most appropriate tools for an artificial liver support.
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PMID:Effects of intraperitoneal transplantation of microcarrier-attached hepatocytes on D-galactosamine-induced acute liver failure in rats. 168 85

Rat liver N-hydroxy-2-acetylaminofluorene (N-OH-2AAF) sulfotransferase activity is mediated by aryl sulfotransferase IV (AST IV) and causes the bioactivation of N-OH-2AAF to a highly reactive sulfuric acid ester form putatively capable of inducing liver cancer. Dietary administration of 2-acetylaminofluorene (2AAF) to induce hepatocarcinogenesis in rats has been shown to cause a rapid loss in N-OH-2AAF sulfotransferase activity. A possible mechanism for the in vivo loss in sulfotransferase activity may be the PAPS-dependent, sulfotransferase-catalyzed, reaction product inactivation of the enzyme by covalent reaction with the N-OH-2AAF sulfuric acid ester. In vitro studies to evaluate this possibility utilized a highly purified form of AST IV and measured the extent of PAPS-dependent interaction between the enzyme and N-OH-2[9-14C]AAF. The results showed the presence of a adenosine-3'-phospho-5'-phosphosulfate (PAPS)-dependent 14C-labeling of AST IV. The labeling could be blocked if the sulfotransferase inhibitor pentachlorophenol was present. Analysis of 14C-labeled AST IV following alkaline digestion and chromatography of digestion products indicated that AST IV cysteine and methionine residues were primary sites of 2[9-14C]AAF adduction. Studies involving the pretreatment of AST IV with PAPS and N-OH-2AAF prior to the measurement of N-OH-2AAF sulfotransferase activity showed a close parallel between formation of the AST IV cysteine-2AAF adduct and loss of activity. Similar studies showed that enzyme inactivation and cysteine-2AAF adduct formation could be blocked when excessive amounts of a competing nucleophile, methionine, were present during the pretreatment step, suggesting that inactivation does not proceed by a mechanism-based process. Finally, experiments involving prior reaction of AST IV with the thiol-blocking agent, N-ethylmaleimide, before measurement of enzyme activity showed essentially full loss of sulfotransferase activity and suggested that formation of AST IV cysteine-2AAF adducts could be a mechanism for enzyme inactivation. These results indicate that the in vitro inactivation of AST IV by the reactive N-OH-2AAF sulfuric acid ester is accompanied by covalent binding to AST IV, possibly through the formation of cysteine-2AAF adducts, and suggests that this mechanism merits further consideration as a basis for the loss of N-OH-2AAF sulfotransferase activity in vivo.
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PMID:Reaction product inactivation of aryl sulfotransferase IV following electrophilic substitution by the sulfuric acid ester of N-hydroxy-2-acetylaminofluorene. 173 62

Two decades of research in ethanol metabolism have culminated in the molecular elucidation of an ethanol-inducible cytochrome P450 (P450IIE1) which is not only involved with ethanol metabolism and ethanol tolerance, but also with the activation of a number of xenobiotics. The unique ability of P450IIE1 to activate xenobiotic agents now appears to be responsible for the increased susceptibility of the heavy drinker to hepatotoxic industrial solvents, commonly used drugs, over-the-counter medications and chemical carcinogens. It also explains some of the interaction of ethanol with nutritional factors, such as hepatic vitamin A: enhanced microsomal degradation of retinoids (together with hepatic mobilisation) promotes depletion. Treatment, however, is complicated by the fact that ethanol also enhances the toxicity of excess vitamin A. All pathways of ethanol metabolism result in the production of acetaldehyde, the toxicity of which has been reviewed (Lieber 1982). New aspects discussed here include the formation of acetaldehyde-protein adducts and an associated immune response that may play a pathogenic role. Also discussed are the implications of ethanol-induced alterations in microtubules, mitochondria and plasma membranes, as they relate, in part, to accompanying acetaldehyde-induced toxicity, to the production of free radicals or to lipid peroxidation-mediated injury associated with glutathione depletion. There is also depletion of S-adenosyl-L-methionine (SAMe). Administration of synthetic SAMe results in a partial correction of the SAMe depletion and a consequent restoration of glutathione levels. Other beneficial effects of SAMe include a significant attenuation of the increase in plasma aspartate transaminase and glutamate dehydrogenase activities. Mitochondrial damage, including giant forms, documented by light and electron microscopy, is also attenuated by SAMe. Thus, the new understanding of the pathophysiology of alcohol-induced liver damage has led to more successful therapy with drugs and nutritional factors.
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PMID:Interaction of alcohol with other drugs and nutrients. Implication for the therapy of alcoholic liver disease. 208 78

Twenty-four hours after acute administration of cocaine HCl (25 mg/kg, i.p.) to male C57BL/6ByJ mice, there was no hepatotoxicity as measured by plasma aspartate aminotransferase (AST) activity. In contrast, daily administration of cocaine (25 mg/kg, i.p.) for 14 days induced marked hepatotoxicity, as characterized by a greater than 400% increase in plasma AST activity when assayed 24 hr after the last injection. Concomitantly, the liver had increased levels of cysteine, gamma-glutamylcysteine, glutathione, cysteinylglycine, glutamate, methionine, taurine, and aspartate. The effect appeared to be selective for compounds of the glutathione metabolic pathways, because repeated cocaine exposure did not affect other amino acids such as leucine, isoleucine, phenylalanine, serine, and valine. There was a positive correlation between the magnitude of the elevation of cysteine and the extent of liver damage. Daily cocaine administration did not affect striatal or frontal cortex glutathione. A final cocaine challenge (50 mg/kg, i.p.) did not affect either hepatic or cerebral glutathione metabolism. The increase in hepatic cysteine and glutathione upon daily cocaine administration is a potentially important compensatory mechanism against cocaine-induced hepatotoxicity.
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PMID:Differential effects of daily administration of cocaine on hepatic and cerebral glutathione in mice. 224 12

1. Glutamine was found to be the main carbon and nitrogen product of the metabolism of aspartate in isolated guinea-pig kidney-cortex tubules. Glutamate, ammonia and alanine were only minor products. 2. Carbon-balance calculations and the release of 14CO2 from [U-14C]aspartate indicate that oxidation of the aspartate carbon skeleton occurred. 3. A pathway involving aspartate aminotransferase, glutamate dehydrogenase, glutamine synthetase, phosphoenolpyruvate carboxykinase, pyruvate kinase, pyruvate dehydrogenase and enzymes of the tricarboxylic acid cycle is proposed for the conversion of aspartate into glutamine. 4. Evidence for this pathway was obtained by: (i) inhibiting aspartate removal by amino-oxyacetate, an inhibitor of transaminases, (ii) the use of methionine sulphoximine, an inhibitor of glutamine synthetase, which induced a large increase in ammonia release from aspartate, (iii) the use of quinolinate, an inhibitor of phosphoenolpyruvate carboxykinase, which inhibited glutamine synthesis from aspartate, (iv) the use of alpha-cyano-4-hydroxycinnamate, an inhibitor of the mitochondrial transport of pyruvate, which caused an accumulation of pyruvate from aspartate, and (v) the use of fluoroacetate, an inhibitor of aconitase, which inhibited glutamine synthesis with concomitant accumulation of citrate from aspartate.
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PMID:Glutamine synthesis from aspartate in guinea-pig renal cortex. 236 82


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