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)

In previous studies it was found that: (a) aspartate aminotransferase increases the aspartate dehydrogenase activity of glutamate dehydrogenase; (b) the pyridoxamine-P form of this aminotransferase can form an enzyme-enzyme complex with glutamate dehydrogenase; and (c) the pyridoxamine-P form can be dehydrogenated to the pyridoxal-P form by glutamate dehydrogenase. It was therefore concluded (Fahien, L.A., and Smith, S.E. (1974) J. Biol. Chem 249, 2696-2703) that in the aspartate dehydrogenase reaction, aspartate converts the aminotransferase into the pyridoxamine-P form which is then dehydrogenated by glutamate dehydrogenase. The present results support this mechanism and essentially exclude the possibility that aspartate actually reacts with glutamate dehydrogenase and the aminotransferase is an allosteric activator. Indeed, it was found that aspartate is actually an activator of the reaction between glutamate dehydrogenase and the pyridoxamine-P form of the aminotransferase. Aspartate also markedly activated the alanine dehydrogenase reaction catalyzed by glutamate dehydrogenase plus alanine aminotransferase and the ornithine dehydrogenase reaction catalyzed by ornithine aminotransferase plus glutamate dehydrogenase. In these latter two reactions, there is no significant conversion of aspartate to oxalecetate and other compounds tested (including oxalacetate) would not substitute for aspartate. Thus aspartate is apparently bound to glutamate dehydrogenase and this increases the reactivity of this enzyme with the pyridoxamine-P form of aminotransferases. This could be of physiological importance because aspartate enables the aspartate and ornithine dehydrogenase reactions to be catalyzed almost as rapidly by complexes between glutamate dehydrogenase and the appropriate mitochondrial aminotransferase in the absence of alpha-ketoglutarate as they are in the presence of this substrate. Furthermore, in the presence of aspartate, alpha-ketoglutarate can have little or no affect on these reactions. Consequently, in the mitochondria of some organs these reactions could be catalyzed exclusively by enzyme-enzyme complexes even in the presence of alpha-ketoglutarate. Rat liver glutamate dehydrogenase is essentially as active as thebovine liver enzyme with aminotransferases. Since the rat liver enzyme does not polymerize, this unambiguously demonstrates that monomeric forms of glutamate dehydrogenase can react with aminotransferases.
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PMID:Effect of aspartate on complexes between glutamate dehydrogenase and various aminotransferases. 1 47

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

Admission serum triiodothyronine (T3) values in 124 patients hospitalized for alcoholic liver disease were correlated with clinical and laboratory indices of liver function and commonly used determinants of thyroid function. Patients with low admission serum T3 levels had significant alterations in serum albumin, bilirubin, prothrombin time, and alkaline phosphatase associated with clinical signs of portal hypertension and collateral circulation, with little difference in serum glutamic-oxaloacetic transaminase, serum gamma glutamyl transpeptidase, or serum ornithine carbamyl transferase. This group also had a significant decrease in free T3 index despite an increase in T3 uptake; the slight reduction in total thyroxine (T4) was associated with an increase in free T4 index and no change in serum thyrotropin (TSH). For patients with alcoholic liver disease, low admission serum T3 and free T3 index values when accompanied by normal serum T4, free T4 index, and TSH levels appear to be indicative of severe liver dysfunction and increased mortality risk.
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PMID:Serum triiodothyronine and other clinical and laboratory indices of alcoholic liver disease. 46 36

The mechanism of inhibition of ornithine aminotransferase [EC 2.6.1.13] by L-canaline (alpha-amino-gamma-amino-oxybutyric acid) was investigated. Spectral changes of pyridoxal 5'-phosphate in ornithine aminotransferase on addition of L-canaline showed that L-canaline formed an oxime-type compound with pyridoxal 5'-phosphate that had the same spectra as the compound formed on addition of hydroxylamine to the holoenzyme. Kinetic studies indicated that hydroxylamine was a reversible noncompetitive inhibitor, whereas L-canaline was an irreversible inhibitor of ornithine aminotransferase. Other analogs, such as delta-aminovaleric acid and alpha-N-acetyl-L-ornithine, also reacted with the pyridoxal 5'-phosphate of the enzyme, but these compounds were competitive inhibitors with respect to L-ornithine. L-Canaline and hydroxylamine also reacted with pyridoxal 5'-phosphate in pig heart aspartate aminotransferase [EC 2.6.1.1] to produce an oxime, but both of them were reversible and noncompetitive inhibitors of the enzyme. The Ki value of hydroxylamine for ornithine aminotransferase was 4.3 X 10(-7) M and those of L-canaline and hydroxylamine for aspartate aminotransferase were 1.7 X 10(-4) M and 2.2 X 10(-5) M, respectively.
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PMID:Mode of inhibition of ornithine aminotransferase by L-canaline. 62 4

In order to assess the extent to which metabolism within the sheep placenta may influence the transfer of metabolites between mother and foetus at different stages of gestation the activities of enzymes concerned with some aspects of carbohydrate, amino acid and keton body metabolism were determined in placental cotyledons resected from ewes during the last three months of pregnancy. The activities of pyruvate kinase (EC 2.7.1.40), lactate dehydrogenase (EC 1.1.1.27), malate dehydrogenase (EC 1.1.1.37), ATP citrate (pro-3S)-lyase (EC 4.1.3.8), citrate (si)-synthase (EC 4.1.3.7), acetyl-CoA synthetase (EC 6.2.1.1), acetyl-CoA acetyltransferase (EC 2.3.1.9) and 3-keto acid CoA-transferase (EC 2.8.3.5) per gram wet weight cotyledon do not change during the period studied. The activities of alanine aminotransferase (EC 2.6.1.2), aspartate aminotransferase (EC 2.6.1.1), isocitrate dehydrogenase (NADP+) (EC 1.1.1.42), ornithine-oxoacid aminotransferase (EC 2.6.1.13) and 3-hydroxybutyrate dehydrogenase (EC 1.1.1.30) show an increase in activity between the third and fourth months of pregnancy whilst the activities of arginase (EC 3.5.3.1) and possibly pyruvate carboxylase (EC 6.4.1.1) show an increase in activity between the fourth and final months of pregnancy. Ornithine decarboxylase (EC 4.1.1.17) activity declines to one tenth of its activity during this later period. The absence of detectable activities of phosphoenolpyruvate carboxykinase (EC 4.1.1.32) and ornithine carbamoyltransferase (EC 2.1.3.3) indicate that gluconeogenesis and urea synthesis from ammonia do not occur in the sheep placenta. It appears that the ability of the placenta to metabolise several substrates is achieved by the time the placenta reaches its maximum size at approximately 90 days.
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PMID:Enzyme activities in the sheep placenta during the last three months of pregnancy. 84 73

The effects of intravenous administration of Escherichia coli endotoxin were studied in eight mature lactating cows. Three cows were studied following intrammary infection with E. coli. Significant clinical findings are presented. Significant clinico-pathological findings include leukopenia, decreased blood serum calcium concentrations and increased levels of serum glutamic-oxaloacetic transaminase and serum ornithine-carbamyl transferase. Significant elevations of plasma corticosteroids were also noted.
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PMID:Clinical and clinico-pathological effects of Escherichia coli endotoxin in mature cattle. 108 61

The activities of ornithine carbamyl transferase, arginase and glutamic-pyruvic transaminase increase in the liver of the rat if the biological value of the dietary protein decreases. Experiments with pigs revealed in the blood serum an analogous high correlation between the biological value of the dietary protein and the activities of arginase, glutamic-pyruvic transaminase, leucine aminopeptidase and glutamic-oxalacetic transaminase. The most favourable possibility of protein evaluation on the basis of criteria of the intermediary protein metabolism consists in the determination of the blood urea concentration provided that the protein carrier supply is standardized. This procedure which has been elaborated by BERGNER and co-workers in 1968 for the determination of the protein quality was confirmed by TAYLOR and co-workers in 1974 on healthy individuals as a reliable and elegant measuring technique with highly significant correlation. It is concluded that the true biological value of protein carriers or protein mixtures which are intended for human nutrition can on principle be determined only in studies with healthy individuals.
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PMID:[Protein evaluation based on intermediary protein metabolism criteria]. 122 18

We have previously reported that a single meal of an arginine-free diet rapidly induces hyperammonemia in young ferrets and that aspirin administration in conjunction with influenza B infection and arginine-free diet results in clinical and biochemical alterations consistent with Reye's syndrome. The objective of the present study was to test whether ibuprofen administration, either alone or in combination with influenza infection and arginine-free diet, produces a similar effect. Two-mo-old ferrets were inoculated intranasally with influenza B virus, treated with therapeutic doses of ibuprofen, and fed a single meal of an arginine-free diet. Arginine-free diet caused a significant increase in plasma ammonia and a small increase in plasma aspartate aminotransferase activity. All ferrets fed an arginine-free diet recovered within 6 to 7 h after ingesting the diet. Ibuprofen treatment, either solely or in combination with influenza infection, did not produce significant change in the plasma levels of aspartate or ornithine aminotransferase activities. A combination of ibuprofen treatment, influenza infection, and arginine-free diet caused a significant increase in the mortality and plasma ammonia levels. Plasma aspartate aminotransferase and ornithine carbamyl transferase activities were elevated, and liver ornithine carbamyl transferase activity was decreased. However, other mitochondrial enzymes such as ornithine aminotransferase were not altered, whereas the activity of cytoplasmic enzymes such as arginase were decreased. These results suggest that ibuprofen administration resulted in generalized hepatopathy rather than specific mitochondrial injury and Reye's syndrome-like changes associated with aspirin in our previous model.
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PMID:Interactions of ibuprofen with influenza infection and hyperammonemia in an animal model of Reye's syndrome. 156 Oct 11

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

Injection with pharmacological doses of dexamethasone (5 mg/kg) and/or bovine glucagon (1 mg/kg) exerts pronounced effects on toadfish liver compared with vehicle-treated control fish. Affected parameters include hepatic levels of glycogen and the activities of glutamate dehydrogenase, aspartate aminotransferase, malate dehydrogenase, and enzymes involved in NADPH generation as well as the kinetics of pyruvate kinase. Activities of tyrosine aminotransferase, however, a prime target for hormonal induction in mammals, remain unchanged in Opsanus. In subsequently isolated toadfish hepatocytes, metabolite concentrations and flux through gluconeogenesis are altered as are in vitro responses to epinephrine and catfish glucagon in previously injected fish. Contrary to existing mammalian models, short-term regulation of urea cycle activity can be ruled out for toadfish, since hormone treatments fail to influence the activity of two ornithine-urea cycle enzymes or the rate of hepatocyte-urea synthesis. Treatment-dependent increases in hepatic glutamine synthetase, the unique feeder enzyme for ammonia "nitrogen" in fish urea cycle, indicate a potentially pivotal role for this enzyme in longer-term regulation of ureogenesis.
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PMID:Metabolic actions of glucagon and dexamethasone in liver of the ureogenic teleost Opsanus beta. 160 Dec 63


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