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)

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

A co-culture system of cerebellar granule cells (glutamatergic neurons) and hepatocytes has been developed. Petri dishes divided in halves by a temporary septum were coated with poly-L-lysine and cerebellar granule cells plated in one of the compartments. Five days later hepatocytes were plated in the other compartment and after 2 days the septum was removed and the two cell types shared the same culture medium for a period of 5 days. During this period of time cultures of neurons and hepatocytes kept separately or in co-culture exhibited identical characteristics with regard to activities of pyruvate kinase and glucokinase (hepatocytes), aspartate aminotransferase (neurons) as well as evoked transmitter release (neurons) and content of cytochrome P-450 (hepatocytes). The results show that it is possible to maintain neurons and hepatocytes in co-culture sharing the same culture medium for a prolonged period of time. Such a system may serve as a pharmacological model to study interactions between liver and brain cells with regard to neuroactive drugs.
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PMID:Characterization of a co-culture system of neurons and hepatocytes. 256 Aug 19

It is well established that caloric restriction extends life span and significantly retards the rate of occurrence of most age-associated degenerative disease processes. A paucity of data exists relative to the mechanisms by which caloric restriction accomplishes these events. We have examined the effect of caloric restriction in rats on several hepatic enzymes of intermediary metabolism. The activities of glycolytic and supporting enzymes including lactate dehydrogenase, pyruvate kinase, sorbitol dehydrogenase, and alcohol dehydrogenase were all decreased in response to caloric restriction. Fructose 1-phosphate aldolase and creatine phosphokinase were not altered. Likewise, enzymes associated with lipid metabolism (malic enzyme and glycerokinase) were reduced (fatty acid synthetase was reduced, but not to a statistically significant degree). Activities of enzymes supporting gluconeogenesis (glutamate oxaloacetate transaminase, tyrosine aminotransferase, glutamate pyruvate transaminase, glutamate dehydrogenase, amino acid oxidase, malate dehydrogenase, and glucose 6-phosphatase) were either unchanged or increased significantly by caloric restriction. Glucagon levels were decreased. Comparisons between young ad libitum fed and older calorically restricted rats revealed similar but not identical metabolic activity. These results suggest that caloric restriction produces an effect on intermediary metabolism, favoring the role of glucagon and glucose synthesis; but limiting the role of insulin and glucose catabolism in the liver. The former observation provides for the efficient support of peripheral tissues and the latter a level of energy production necessary only for self maintenance. Limited lipid metabolism suggests decreased potential for fatty acid epoxide formation and free radical damage to cellular macromolecules. Additionally, caloric restriction may delay the progressive age associated changes in the activities of some of the enzymes investigated.
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PMID:Effect of chronic caloric restriction on hepatic enzymes of intermediary metabolism in the male Fischer 344 rat. 266 33

Energy metabolism in proliferating cultured rat thymocytes was compared with that of freshly prepared non-proliferating resting cells. Cultured rat thymocytes enter a proliferative cycle after stimulation by concanavalin A and Lymphocult T (interleukin-2), with maximal rates of DNA synthesis at 60 h. Compared with incubated resting thymocytes, glucose metabolism by incubated proliferating thymocytes was 53-fold increased; 90% of the amount of glucose utilized was converted into lactate, whereas resting cells metabolized only 56% to lactate. However, the latter oxidized 27% of glucose to CO2, as opposed to 1.1% by the proliferating cells. Activities of hexokinase, 6-phosphofructokinase, pyruvate kinase and aldolase in proliferating thymocytes were increased 12-, 17-, 30- and 24-fold respectively, whereas the rate of pyruvate oxidation was enhanced only 3-fold. The relatively low capacity of pyruvate degradation in proliferating thymocytes might be the reason for almost complete conversion of glucose into lactate by these cells. Glutamine utilization by rat thymocytes was 8-fold increased during proliferation. The major end products of glutamine metabolism are glutamate, aspartate, CO2 and ammonia. A complete recovery of glutamine carbon and nitrogen in the products was obtained. The amount of glutamate formed by phosphate-dependent glutaminase which entered the citric acid cycle was enhanced 5-fold in the proliferating cells: 76% was converted into 2-oxoglutarate by aspartate aminotransferase, present in high activity, and the remaining 24% by glutamate dehydrogenase. With resting cells the same percentages were obtained (75 and 25). Maximal activities of glutaminase, glutamate dehydrogenase and aspartate aminotransferase were increased 3-, 12- and 6-fold respectively in proliferating cells; 32% of the glutamate metabolized in the citric acid cycle was recovered in CO2 and 61% in aspartate. In resting cells this proportion was 41% and 59% and in mitogen-stimulated cells 39% and 65% respectively. Addition of glucose (4 mM) or malate (2 mM) strongly decreased the rates of glutamine utilization and glutamate conversion into 2-oxoglutarate by proliferating thymocytes and also affected the pathways of further glutamate metabolism. Addition of 2 mM-pyruvate did not alter the rate of glutamine utilization by proliferating thymocytes, but decreased the rate of metabolism beyond the stage of glutamate significantly. Formation of acetyl-CoA in the presence of pyruvate might explain the relatively enhanced oxidation of glutamate to CO2 (56%) by proliferating thymocytes.
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PMID:Glutamine and glucose metabolism during thymocyte proliferation. Pathways of glutamine and glutamate metabolism. 286 9

In lymphocytes of the rat, pyruvate kinase, phosphoenolpyruvate carboxykinase and NADP+-linked malate dehydrogenase (decarboxylating) are distributed almost exclusively in the cytosol whereas pyruvate carboxylase is distributed almost entirely in the mitochondria. For NAD+-linked malate dehydrogenase and aspartate aminotransferase approximately 80% and 40%, respectively, are in the cytosolic compartment. Since glutaminase is present in the mitochondria, glutamine is converted to malate within the mitochondria but further metabolism of the malate is likely to occur in the cytosol. Hence pyruvate produced from this malate, via oxaloacetate and phosphoenolpyruvate carboxykinase, may be rapidly converted to lactate, so restricting the entry of pyruvate into the mitochondria and explaining why very little glutamine is completely oxidised in these cells despite a high capacity of the Krebs cycle.
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PMID:Intracellular distribution of some enzymes of the glutamine utilisation pathway in rat lymphocytes. 374 15

Human red blood cells were separated by a discontinuous Percoll density gradient into fractions of increasing density. Red cells comprising the lowest and highest density fractions, respectively, were subsequently separated according to mean cell volume (MCV) by means of counterflow centrifugation. The activities of 4 red cell age-dependent enzymes (hexokinase (HK), pyruvate kinase (PK), glucose-6-phosphate dehydrogenase (G6PD) and aspartate aminotransferase (ASAT) were highest in the red cell fraction with low density/large MCV, although the difference from red cell enzyme activities in the total low density fraction was not significant. These 4 enzyme activities were lowest in the fraction of red cells with high density/small MCV. The relative activities of the enzymes in the high density/small MCV fraction, as compared to the unseparated cell population, were: HK (58%), PK (49%), G6PD (53%) and ASAT (28%). These activities were all significantly lower than those measured in the total high density red cell fraction. The rates of lactate production in the low density/large MCV cells (0.89 +/- 0.15 mumol X min-1 X 10(-11) cells) is approximately 3-fold higher than in high density/small MCV cells (0.33 +/- 0.03 mumol X min-1 X 10(-11) cells). This latter value is 1.8-fold lower than the rate of lactate production in the total high density red cell fraction (0.59 +/- 0.14 mumol X min-1 X 10(-11) cells) and is, in contrast to lactate production in other density/size fractions, insensitive to phosphate as a metabolic stimulus. It is argued that the combination of density gradient and counter-flow centrifugation offers a greater potential for obtaining an old red cell population than classical red cell density centrifugation alone.
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PMID:Glycolytic activity in human red cell populations separated by a combination of density and counterflow centrifugation. Evidence for an improved separation of red cells according to age. 378 70

The sequence of inactivation of five bovine erythrocyte enzymes (glucose-6-phosphate dehydrogenase, pyruvate kinase, lactate dehydrogenase, aspartate aminotransferase and aldolase) was compared during in vivo aging of the red blood cell and during treatment of the cells with heat, gamma-radiation and an enzymatic source of the superoxide radical anion. Amounts of oxygen free radicals comparable to those formed physiologically in the cells were able to induce considerable inactivation of some enzymes; in no case was the physiological sequence of inactivation reproduced. These results seem to argue for a multifactorial inactivation of red cell enzymes during intravascular aging of the erythrocyte.
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PMID:Aging of the erythrocyte. VII. On the possible causes of inactivation of red cell enzymes. 689 33

The effects of a high fat diet (30% (w/w) corn oil) on chronic streptozotocin-diabetic rats were investigated at the whole body level and at the enzyme level. The diet caused significant decreases in the extent of polydipsia (66% decrease), polyphagia (49%), polyuria (67%) and glycosuria (70%). The activities of selected hepatic enzymes from the glycolytic, gluconeogenic, ureogenic and lipogenic clusters were determined. The fat diet caused significant decreases (range: 47 to 54%) in the activity of the ureogenic enzymes carbamyl phosphate synthetase, ornithine transcarbamylase and arginase; had no effect on the glycolytic enzymes glucokinase, hexokinase and pyruvate kinase; partially decreased the diabetes-induced elevated activities of the gluconeogenic enzymes phosphoenolpyruvate carboxykinase (63% decrease), serine dehydratase (90%), alanine aminotransferase (31%) and aspartate aminotransferase (65%), and partially reversed the activity of one lipogenic enzyme, ATP citrate lyase.
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PMID:The effects of a high fat diet on chronic streptozotocin-diabetic rats. 692 68

The activity of serum enzymes, such as, creatine kinase (CK), pyruvate kinase (PK), aldolase (ALD), lactate dehydrogenase (LDH), sorbitol dehydrogenase (SbDH), malate dehydrogenase (MDH), glutamate-aspartate aminotransferase (AST), glutamate-alanine aminotransferase (ALT), myokinase (MK), glucosephosphate isomerase (GPI), alkaline phosphatase (AlkP), pseudocholinesterase (PsCHE) isocitrate dehydrogenase and gamma-glutamyltranspeptidase (gamma-GTP), was determined in 256 patients with progressing myodystrophy (PMD) (Duchenne's form in 125, Becker's form in 14, pelvicohumeral form in 36, humeroscapulofacial form in 19, ocular form in 10, other rare forms in 34, and nonidentified forms in 13 patients). In the control group (64 men, 56 women and 50 children), the activity of the enzymes was found to depend on the patients' sex and age. With regard to both parameters, i. e. the degree of the enzyme activity rise and the frequency of the pathological values the most informative were CK, then PK and ALD, and then all the other enzymes. Of all the PMD forms the enzymatic activity appeared to be the highest in patients with the pseudohypertrophic malignant form. By determining the activity of five enzymes (CK, ALD, LDH, AST and ALT) and taking into consideration the patient's age, the onset and the duration of the disease one can distinguish between sick and healthy subjects, as well as between various forms of PMD.
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PMID:[Serum enzyme dynamics in progressive muscular dystrophies]. 703 17

The effect of 90% jejunoileal bypass procedure on liver enzymes was evaluated in 11 obese Zucker fat rats after a 50% weight loss. Control tissues were also collected from 11 unoperated obese rats. In the jejunoileal bypass group, there was a significant decrease in phosphofructokinase, pyruvate kinase, and glucose-6-phosphate dehydrogenase activities. Pyruvate carboxylase, alanine aminotransferase, and lactate dehydrogenase activities were not altered. Fructose 1,6-biphosphatase, aldolase, aspartate aminotransferase, and phosphoenolpyruvate carboxykinase activities were increased in the jejunoileal bypass group. These studies suggest that after jejunoileal bypass glycolysis is reduced and gluconeogenesis is increased. Amino acids may provide an essential energy source for hepatic function.
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PMID:Changes in hepatic carbohydrate metabolism after jejunoileal bypass. 707 18


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