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)

We evaluated the concept that the vascular entrance of both bacterial and nonbacterial particulate material could lead to hepatic parenchymal cell injury, either due to postphagocytic Kupffer cell activity or the margination of activated leukocytes in the liver. Injection of denatured, collagen-coated particles as well as heat-killed bacteria were used as particulate challenges. Hepatic parenchymal cell injury in vivo during postoperative sepsis was evaluated by plasma aspartate aminotransferase (AST) and ornithine carbamyl transferase (OCT) enzyme levels over 3-72 h. AST and OCT levels elevated following either laparotomy plus cecal ligation (mild sepsis) or laparotomy plus cecal ligation with puncture (severe sepsis), with the peak level at 24 h. In addition, the direct intravenous injection of either nonbacterial foreign particles or heat-killed Pseudomonas aeruginosa into normal rats also produced a dose-dependent elevation of AST and OCT. The plasma level of either AST or OCT actually increased 350-400% after injection of the non-bacterial particles. A similar dose related elevation in enzymes followed the intravenous injection of heat-killed Pseudomonas. To differentiate the potential contribution of activated hepatic Kupffer cells versus activated marginated neutrophils to the in vivo hepatic injury, we determined the release of the hepatic specific enzyme OCT by cultured hepatic parenchymal cells when they were exposed to isolated Kupffer cells or isolated PMNs that were activated by exposure to dead bacteria. Bacteria alone when added to cultured hepatocytes did not induce significant OCT release. In contrast, activated PMNs but not Kupffer cells induced a significant (p less than 0.05) release of OCT from parenchymal cells into the culture media. Thus, in vivo transient hepatic parenchymal cell injury with post-operative sepsis may be mediated by the margination of activated PMNs in the liver.
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PMID:Hepatocyte injury during post-operative sepsis: activated neutrophils as potential mediators. 342 80

Malate dehydrogenase (EC 1.1.1.37) and aspartate aminotransferase (EC 2.6.1.1) are present in porcine blood platelets in both mitochondria and the cytosol. The latter enzyme is inhibited in a typical way by aminooxycompounds and cycloserine. Blocking of aminotransferase or inhibition of the mitochondrial dicarboxylate carrier by butylmalonate stimulates lactate production by intact platelets and inhibits their aggregation induced by ADP or collagen. These results indicate that the reoxidation of cytosolic NADH via the malate-aspartate shuttle is important for covering the energy demand of platelets necessary for their stimulation.
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PMID:Importance of the malate-aspartate shuttle for the reoxidation of glycolytically produced NADH and for cell aggregation in porcine blood platelets. 368 99

In bovine platelets aspartate aminotransferase has a high activity. The enzyme in vitro is inhibited in a dose dependent manner by aminooxyacetate (IC50 = 10(-4) M), hydroxylamine (IC50 = 10(-4) M), and cycloserine (IC50 = 5 X 10(-3). The inhibitory effect of all the three compounds is strongest at low substrate (aspartate) concentration. Blocking of aspartate aminotransferase activity by these compounds in intact platelets is accompanied by the inhibition of ADP and collagen-induced aggregation. Among the three compounds the strongest inhibitor of platelet aggregation was hydroxylamine, which was also the most effective inhibitor of aspartate aminotransferase. Other metabolic blockers, i.e. dinitrophenol (DNP), rotenone and antimycin also inhibited the aggregation of platelets, and a synergism has been demonstrated between DNP, rotenone and antimycin A action on platelet aggregation and blockade of aspartate aminotransferase activity. The results are interpreted to mean that transamination is of importance in the energy production in the activated platelet, probably through its participation in reducing equivalents transport from the cytosol to the mitosol via the malate: oxaloacetate: aspartate shuttle.
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PMID:The importance of aspartate aminotransferase for platelet aggregation. 375 38

To study the effect of facilitated diffusion of the intermediate metabolite, oxaloacetate, on the coupled reaction of aspartate aminotransferase (L-aspartate: 2-oxoglutarate aminotransferase, EC 2.6.1.1) and malate dehydrogenase (L-malate:NAD+ oxidoreductase, EC 1.1.1.37), these enzymes were co-immobilized on the surface of a collagen film. The kinetic properties of the immobilized enzymes were compared with those observed with the enzymes in solution. Since the reactions correspond to the cytosolic enzymes, they have been studied in the direction aspartate aminotransferase toward malate dehydrogenase. Coupled enzymes in solution showed classical behaviour. A lag-time was observed before they reached a steady state and this lag-time was dependent on the kinetic properties of the second enzyme, malate dehydrogenase. The same lag-time was observed when malate dehydrogenase in solution was coupled with aspartate aminotransferase bound to the film. When aspartate aminotransferase in solution was coupled with malate dehydrogenase bound to the collagen film, a very long lag-time was observed. Theoretical considerations showed that in the latter case, the lag-time was dependent on the kinetic properties of the second enzyme and the transport coefficient of the intermediate substrate through the boundary layer near the surface of the film. Then both enzymes were co-immobilized on the collagen film. The coupled activity of aspartate aminotransferase and malate dehydrogenase was compared for films with an activity ratio of 5 and 0.8. In both cases, a highly efficient coupling was observed. In the former case, where malate dehydrogenase was rate-limiting, 81% of this limiting activity was observed. In the latter case, aspartate aminotransferase was rate-limiting and 82% of its rate was obtained for the final product formation. The linear increase of product formation with time corresponded fairly well to the theoretical equations developed in the paper. To interpret these rate equations, one should assume that the intermediate substrate oxaloacetate formed by aspartate aminotransferase was used by malate dehydrogenase in the diffusion layer near the film, before diffusing in the bulk solution.
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PMID:Coupled reaction of immobilized aspartate aminotransferase and malate dehydrogenase. A plausible model for the cellular behaviour of these enzymes. 399 45

1. The rat uterus contains acid cathepsin, beta-glucuronidase, beta-galactosidase, acid phosphatase and deoxyribonuclease II at concentrations comparable with those found in liver. Two non-hydrolytic uterine enzymes, cytochrome c oxidase and aspartate aminotransferase, display only 2-6% of the activity found in liver. 2. The concentrations of acid cathepsin and beta-glucuronidase are significantly decreased in pregnancy and increase 3-4-fold during post-partum involution. 3. The concentrations of beta-galactosidase and acid phosphatase are not decreased in pregnancy and increase only 2-3-fold during involution. 4. The concentrations of these four acid hydrolases increase linearly during the first 4 days post partum and reach their peak values at the same time that wet weight and collagen content fall to their lowest point. 5. The concentration of deoxyribonuclease is depressed in pregnancy but does not rise above normal in the post-partum period. 6. Only a small proportion of each hydrolytic activity can be isolated in the mitochondrial-lysosomal fraction of sucrose homogenates of the rat uterus. This proportion increases during involution. However, the extensive mitochondrial rupture occurring during homogenization indicates that the technique is probably too harsh to obtain a true measure of the proportion of lysosomes present in the intact tissue. 7. There are no significant changes in either the concentration or subcellular distribution of the five acid hydrolases in the livers of the experimental rats during pregnancy or involution. In each case the largest proportion of the activity is found in the mitochondrial-lysosomal fraction of liver homogenates. 8. The results are interpreted in terms of the lysosomal theory of intracellular digestion.
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PMID:Acid hydrolases of the rat uterus in relation to pregnancy, post-partum involution and collagen breakdown. 589 45

The activities of prolyl hydroxylase (Pro-OHase), galactosylhydroxylysyl glucosyltransferase (Glu-Gal-Hyl-Tase), and hydroxylysyl galactosyltransferase (Gal-Hyl-Tase) were assayed in lung tissues of hamsters with bleomycin-induced experimental pulmonary fibrosis. Serum Glu-Gal-Hyl-Tase and aspartate transaminase (Asp-NH2-Tase) were measured in the same animals. Lung fibrosis was induced by intratracheal bleomycin instillation, and the enzyme activities were assayed 2, 3, and 4 weeks after bleomycin administration. The activities of the three lung enzymes increased significantly after bleomycin instillation. However, no difference in the values of serum Glu-Gal-Hyl-Tase or Asp-NH2-Tase were observed. Histologic examination of lung sections indicated progressive fibrotic foci. These results thus indicate that the activities of collagen processing enzymes are elevated in the fibrotic lung tissues as a reflection of the increased rate of collagen synthesis during the period of active fibrogenesis, but unlike liver fibrosis, the elevation of tissue Glu-Gal-Hyl-Tase is not predicted by a corresponding increase in serum levels of this enzyme.
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PMID:Enzymes of collagen synthesis in lung tissues of bleomycin-induced pulmonary fibrosis. 620 Sep 53

An experimental animal model designed specifically to simulate liver fibrosis and cirrhosis in childhood is described. Phenobarbitone was administered continuously from the 4th day of life and carbon tetrachloride intermittently from the 13th day to developing rats for 10 weeks. Treated animals showed hepatic necrosis, hepatic regeneration and a progressive increase in hepatic fibrosis; cirrhosis developed before the animals reached sexual maturity at 72 days or were fully grown. Hepatic prolyl hydroxylase activity increased to a maximum level after 20 days of treatment, before increased hepatic collagen could be detected, and fell to a lower level as cirrhosis became established. Serum activities of alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase gave a similar pattern, a marked increase at 20 days of age followed by a fall to near normal levels as hepatic damage became more severe. By the 26th day of life hepatic collagen levels were increased significantly and rose thereafter progressively as fibrosis became more widespread throughout the liver. Cirrhosis developed between the 38th and 75th days. Cirrhosis remained 10 weeks after discontinuation of treatment with phenobarbitone and carbon tetrachloride treatment.
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PMID:Carbon tetrachloride-induced hepatic fibrosis and cirrhosis in the developing rat: an experimental model of cirrhosis in childhood. 630 21

Alcoholic and, to a lesser extent, nonalcoholic patients with liver disease have serum antibodies to acetaldehyde-protein adducts produced in vitro. These antibodies presumably reflect the presence of adducts in the liver, but the protein that triggers this immune response has not been identified. To study this, we measured the reactivity of cytosolic proteins to rabbit IgG developed against a P-450 2E1-acetaldehyde adduct, isolated from alcohol-fed rats, that recognizes acetaldehyde-modified epitopes in proteins. Adducts were determined on Western blots by scanning densitometry of antibody-linked alkaline phosphatase activity in 4 normal livers and in needle biopsy specimens from subjects with liver disease, 17 alcoholic and 14 nonalcoholic. In all livers, except for a normal one, we found a reactive protein of at least 200 kD, similar to the collagen-acetaldehyde adduct we reported to be markedly increased in rats with experimentally induced cirrhosis. The immunostaining intensity in the alcoholic patients with liver disease was eightfold (p < 0.01) and that in nonalcoholic patients with liver disease was fourfold, greater (p < 0.02) than the weak staining in normal livers; it correlated with the degree of inflammation and serum AST or gamma-glutamyl transpeptidase activities. The adduct was reproduced on incubation of normal cytosolic proteins with 2.5 mmol/L acetaldehyde, whereas higher concentrations yielded many additional adducts; the adduct also reacted with IgG antibody to rat collagen type I and disappeared after digestion with collagenase, suggesting that the target protein is a form of collagen.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Collagen-acetaldehyde adducts in alcoholic and nonalcoholic liver diseases. 791 86

Serum levels of the tissue inhibitor of metalloproteinases-1 (TIMP-1) were measured in 268 patients with liver diseases by means of a one-step sandwich enzyme immunoassay. In the cases of acute hepatitis, chronic active hepatitis (CAH), liver cirrhosis (LC) and hepatocellular carcinoma (HCC), the levels of TIMP-1 were higher than those of the control group. Tissue inhibitor of metalloproteinases-1 levels correlated with type III procollagen peptide and with type IV collagen, indicating TIMP-1 as a useful marker for hepatic fibrosis. Levels of TIMP-1 also correlated with aspartate aminotransferase and alanine aminotransferase levels and showed the highest levels in acute hepatitis. Thus, TIMP-1 might also reflect hepatic inflammation. Serum levels of alpha-fetoprotein and TIMP-1 had a significant positive correlation in patients with HCC. A cut-off level of TIMP-1 between LC and HCC was set at 440 ng/mL, having a low sensitivity and a high specificity. These results suggest the usefulness of TIMP-1 as a tumour marker in cases of HCC where alpha-fetoprotein levels are not elevated.
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PMID:Clinical evaluation of serum tissue inhibitor of metalloproteinases-1 levels in patients with liver diseases. 821 91

Tissue iron loading in hypotransferrinaemic (hpx/hpx) mice was investigated as a model for genetic (primary) haemochromatosis. Iron loading of liver preceded that in the pancreas and heart. One-year-old hpx/hpx mice showed iron staining in exocrine pancreas, liver parenchymal cells, and cardiac and intestinal smooth muscle cells. Iron-loaded macrophages were observed in all these tissues. Islets of Langerhans, biliary epithelial cells, and spleen were iron-free. The pancreas was fibrotic with massive macrophage infiltration and loss of secretory epithelium. Liver showed evidence of chronic inflammatory infiltration with increased collagen fibres in the parenchymal region but no cirrhosis. Serum aspartate aminotransferase activity and plasma glucose were increased in hpx/hpx compared with wild-type mice. Heavy iron loading with haemosiderin deposition in the liver could be demonstrated in hpx/hpx mice from 6 weeks of age. Heterozygous hypotransferrinaemic mice showed minor increases in liver iron stores at 6-12 weeks, but not at 1 year of age. Serum ferritin levels in heterozygous mice were also increased at 6-8 weeks of age. It was concluded that 1-year-old hpx/hpx mice showed evidence of liver and pancreatic damage secondary to tissue iron overload. The iron loading pattern and tissue damage showed some features which were distinct from those observed in haemochromatosis.
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PMID:Tissue iron loading and histopathological changes in hypotransferrinaemic mice. 827 72


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