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)

We measured amino acid contents in the brains of 11 patients with dominantly inherited cerebellar disorders. Despite clinical similarities, three biochemically different disorders were found. One disorder, with demonstrated HLA linkage in one pedigree, was characterized by moderate reduction of aspartate and glutamate contents in cerebellar cortex alone. In a second disorder, aspartate and glutamate contents were reduced markedly in other brain areas as well as in cerebellar cortex. Aspartate and glutamate contents were normal in cerebellar cortex in the third disorder. GABA content in cerebellar cortex and dentate nucleus was reduced in some patients with each disorder, whereas cerebellar taurine content was normal in all patients. Aspartate deficiency in cerebellar cortex did not result from lack of aspartate aminotransferase or pyruvate carboxylase activity. These amino acid abnormalities probably imply loss of specific cerebellar neurons.
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PMID:Neurotransmitter amino acids in dominantly inherited cerebellar disorders. 611 Oct 44

The activity and some kinetic parameters of the key enzymes of the glycolysis, the gluconeogenesis and the amino acid catabolism from the liver of male and female mink have been determined and compared to the corresponding activities from rat and cat. The activities of glucose-6-phosphatase and pyruvate kinase are dependent on sex, both being higher in females. Except for pyruvate carboxylase the glycolytic and the gluconeogenic enzyme activities of the mink are higher than those of rat and cat; especially the activities of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase are markedly higher. The activities of glutamate dehydrogenase and glutamate oxaloacetate transaminase are smaller than the corresponding activities of rat but higher than those of cat. The results suggest that mink has a high capacity for gluconeogenesis compared to rat.
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PMID:Activities of carbohydrate and amino acid metabolizing enzymes from liver of mink (Mustela vison) and preliminary observations on steady state kinetics of the enzymes. 758 47

The effects of cortisol on hepatic and renal gluconeogenic enzyme activities were investigated in sheep fetuses during late gestation and after experimental manipulation of plasma cortisol levels by fetal adrenalectomy and exogenous infusion of cortisol. Hepatic and renal gluconeogenic enzyme activities increased with increasing gestational age in parallel with the normal rise in fetal cortisol levels towards term (146 +/- 2 days). For the majority of enzymes this increase in activity towards term was prevented when the prepartum cortisol surge was abolished by fetal adrenalectomy and stimulated prematurely in fetuses younger than 130 days by exogenous infusion of cortisol. When the data from all the fetuses were combined irrespective of treatment or gestational age, there were significant positive correlations between the log plasma cortisol concentration in utero and the activities of glucose-6-phosphatase, fructose diphosphatase, phosphoenolpyruvate carboxykinase and aspartate transaminase in the fetal liver and kidney, and pyruvate carboxylase in the fetal liver but not in the kidney. No correlation was observed between log plasma cortisol and alanine aminotransferase activity in either fetal liver or kidney. These findings show that cortisol is a physiological regulator of most of the fetal gluconeogenic enzymes and enhances the glucogenic capacity of the sheep fetus during late gestation.
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PMID:The effects of cortisol on hepatic and renal gluconeogenic enzyme activities in the sheep fetus during late gestation. 832 49

Although pyruvate carboxylase associated with both mitochondrial aspartate aminotransferase and malate dehydrogenase, it had a higher affinity for the amino-transferase. Furthermore, the aminotransferase enhanced dissociation of malate dehydrogenase from pyruvate carboxylase. Glutamate dehydrogenase did not associate with pyruvate carboxylase alone, but it apparently associated with the pyruvate carboxylase-aminotransferase complex, and malate dehydrogenase associated with the resulting ternary complex. Citrate synthase and other proteins tested did not associate with pyruvate carboxylase. However, citrate synthase associated with the pyruvate carboxylase-malate dehydrogenase complex. Apparently as a consequence of these heteroenzyme interactions, the rate of the pyruvate carboxylase reaction was slightly greater when coupled with malate dehydrogenase or both malate dehydrogenase and citrate synthase than when coupled with citrate synthase alone. In addition, in the presence of both coupling enzymes, the rate of conversion of pyruvate to citrate was higher than predicted on the basis of the Michaelis-Menten relationship of the two coupling enzymes. Therefore, binding of malate dehydrogenase to pyruvate carboxylase enhances pyruvate carboxylase activity. Association of citrate synthase with the malate dehydrogenase-pyruvate carboxylase binary complex does not alter activation of pyruvate carboxylase but results in citrate synthase being more reactive than free citrate synthase with oxalacetate.
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PMID:Interactions between pyruvate carboxylase and other mitochondrial enzymes. 834 77

(13)C NMR monitored the dynamics of exchange from specific hydrogens of hepatic [2-(13)C]glutamate and [3-(13)C]aspartate with deuterons from intracellular heavy water providing information on alpha-ketoglutarate/glutamate exchange and subcellular compartmentation. Mouse livers were perfused with [3-(13)C]alanine in buffer containing or not 50% (2)H(2)O for increasing periods of time (1 min < t < 30 min). Liver extracts prepared at the end of the perfusions were analyzed by high resolution (13)C NMR (150.13 MHz) with (1)H decoupling only and with simultaneous (1)H and (2)H decoupling. (13)C-(2)H couplings and (2)H-induced isotopic shifts observed in the glutamate C2 resonance, allowed to estimate the apparent rate constants (forward, reverse; min(-1)) for (i) the reversible exchange of [2-(13)C]glutamate H2 as catalyzed mainly by aspartate aminotransferase (0.32, 0.56), (ii) the reversible exchange of [2-(13)C]glutamate H3(proS) as catalyzed by NAD(P) isocitrate dehydrogenase (0.1, 0.05), and (iii) the irreversible exchanges of glutamate H3(proR) and H3(proS) as catalyzed by the sequential activities of mitochondrial aconitase and NAD isocitrate dehydrogenase of the tricarboxylic acid cycle (0.035), respectively. A similar approach allowed to determine the rates of (1)H-(2)H exchange for the H2 (0.4, 0.5) or H3(proR) (0.3, 0.2) or the H2 and H3(proS) hydrogens (0.20, 0.23) of [3-(13)C]aspartate isotopomers. The ubiquitous subcellular localization of (1)H-(2)H exchange enzymes and the exclusive mitochondrial localization of pyruvate carboxylase and the tricarboxylic acid cycle resulted in distinctive kinetics of deuteration in the H2 and either or both H3 hydrogens of [2-(13)C]glutamate and [3-(13)C]aspartate, allowing to follow glutamate and aspartate trafficking through cytosol and mitochondria.
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PMID:Hydrogen turnover and subcellular compartmentation of hepatic [2-(13)C]glutamate and [3-(13)C]aspartate as detected by (13)C NMR. 1174 18

Nutrient secretagogues can increase the production of succinyl-CoA in rat pancreatic islets. When succinate esters are the secretagogue, succinyl-CoA can be generated via the succinate thiokinase reaction. Other secretagogues can increase production of succinyl-CoA secondary to increasing alpha-ketoglutarate production by glutamate dehydrogenase or mitochondrial aspartate aminotransferase followed by the alpha-ketoglutarate dehydrogenase reaction. Although secretagogues can increase the production of succinyl-CoA, they do not increase the level of this metabolite until after they decrease the level of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA). This suggests that the generated succinyl-CoA initially reacts with acetoacetate to yield acetoacetyl-CoA plus succinate in the succinyl-CoA-acetoacetate transferase reaction. This would be followed by acetoacetyl-CoA reacting with acetyl-CoA to generate HMG-CoA in the HMG-CoA synthetase reaction. HMG-CoA will then be reduced by NADPH to mevalonate in the HMG-CoA reductase reaction and/or cleaved to acetoacetate plus acetyl-CoA by HMG cleavage enzyme. Succinate derived from either exogenous succinate esters or generated by succinyl-CoA-acetoacetate transferase is metabolized to malate followed by the malic enzyme reaction. Increased production of NADPH by the latter reaction then increases reduction of HMG-CoA and accounts for the decrease in the level of HMG-CoA produced by secretagogues. Pyruvate carboxylation catalyzed by pyruvate carboxylase will supply oxaloacetate to mitochondrial aspartate aminotransferase. This would enable this aminotransferase to supply alpha-ketoglutarate to the alpha-ketoglutarate dehydrogenase complex and would, in part, account for secretagogues increasing the islet level of succinyl-CoA after they decrease the level of HMG-CoA. Mevalonate could be a trigger of insulin release as a result of its ability to alter membrane proteins and/or cytosolic Ca(2+). This is consistent with the fact that insulin secretagogues decrease the level of the mevalonate precursor HMG-CoA. In addition, inhibitors of HMG-CoA reductase interfere with insulin release and this inhibition can be reversed by mevalonate.
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PMID:The succinate mechanism of insulin release. 1219 57

A flux analysis model for the metabolism of neurotransmitter glutamate is constructed, in order to study functional aspects of its metabolism. This work is based on the potassium [K(+)] evoked neurotransmitter glutamate released, as measured in a series of experiments of superfused rat or mouse brain preparations. These measurements are combined with data reported, concerning the metabolism of glutamate and its precursors, glutamine and glucose in rat cerebral cells in vivo. The proposed stoichiometry of the specific reaction network renders the model solvable. The classification procedure establishes that the measured fluxes are all balanceable and all non-measured fluxes can be calculated. The system is well posed with a condition number of 7.8536. The results emphasize the importance of phosphate activated glutaminase and aspartate aminotransferase in the metabolism of neurotransmitter glutamate. Reported data on the rate of the malate-aspartate shuttle, as well as the anaplerotic flux of the glial pyruvate carboxylase reaction are in agreement with the estimations calculated from the proposed model.
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PMID:Metabolic flux analysis as a tool for the elucidation of the metabolism of neurotransmitter glutamate. 1294 54

The purpose of this study was to examine the effects of chronic exercise training (running 30 m/min, 10% grade, 90 min/d for 8-10 weeks) on specific renal enzyme activities involved with the gluconeogenic pathway in the fed and 24-hr fasted state in rats. A portion of the kidney (containing the cortex and medulla) was homogenized from which cytosolic (c) and mitochondrial (m) fractions were separated. Maximal gluconeogenic enzyme activities were assessed for: phosphoenolpyruvate carboxykinase (cPEPCK), fructose 1,6-bisphosphatase (cFBP), pyruvate carboxylase (mPC), aspartate aminotransferase (cAspAT), alanine aminotransferase (cAlaAT), and lactate dehydrogenase (cLDH). In the fed state, there was no significant difference between groups in any of the enzymes examined (nmoles/min x mg protein-1): cPEPCK (25.8+/- 1.7), cFBP (106.8+/- 7.1), mPC (20.7+/- 1.8), cAspAT (1047.1 +/- 38.6), cAlaAT (52.3 +/- 4.3), and cLDH (1728.6+/- 163.2). After the 24-hr fast, there was a significant increase in cPEPCK (52.4+/- 2.9 and 52.0 +/- 2.1) and mPC (44.6 +/- 4.3 and 47.6 +/- 4.9), control and trained, respectively. These results suggest that the maximal enzyme activities for cPEPCK and mPC can be augmented as a result of fasting that was independent of the training status.
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PMID:Effect of endurance training and fasting on renal gluconeogenic enzymes in the rat. 1525 92

We demonstrate a facile blue native polyacrylamide gel electrophoresis (BN-PAGE) technique to detect two malate-generating enzymes, namely fumarase (FUM), malate synthase (MS) and four oxaloacetate-forming enzymes, namely pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK), citrate lyase (CL) and aspartate aminotransferase (AST). Malate dehydrogenase (MDH) was utilized as a coupling enzyme to detect either malate or oxaloacetate in the presence of their respective substrates and cofactors. The latter four oxaloacetate-forming enzymes were identified by 2,6-dichloroindophenol (DCIP) and p-iodonitrotetrazolium (INT) while the former two malate-producing enzymes were visualized by INT and phenazine methosulfate (PMS) in the reaction mixtures, respectively. The band formed at the site of enzymatic activity was easily quantified, while Coomassie staining provided information on the protein concentration. Hence, the expression and the activity of these enzymes can be readily evaluated. A two-dimensional (2D) BN-PAGE or SDS-PAGE enabled the rapid purification of the enzyme of interest. This technique also provides a quick and inexpensive means of quantifying these enzymatic activities in normal and stressed biological systems.
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PMID:Blue native polyacrylamide gel electrophoresis and the monitoring of malate- and oxaloacetate-producing enzymes. 1615 36

Activities of key enzymes of the Calvin cycle and C(4) metabolism, rates of CO(2) fixation, and the initial products of photosynthetic (14)CO(2) fixation were determined in the podwall, seed coat (fruiting structures), and the subtending leaf (leaf below a receme) of Brassica campestris L. cv ;Toria.' Compared to activities of ribulose-1,5-bisphosphate carboxylase and other Calvin cycle enzymes, e.g. NADP-glyceraldehyde-3-phosphate-dehydrogenase and ribulose-5-phosphate kinase, the activities of phosphoenol pyruvate carboxylase and other enzymes of C(4) metabolism, viz. NADP-malate dehydrogenase, NADP-malic enzyme, glutamate pyruvate transaminase, and glutamate oxaloacetate transaminase, were generally much higher in seed than in podwall and leaf. Podwall and leaf were comparable to each other. Pulse-chase experiments showed that in seed the major product of (14)CO(2) assimilation was malate (in short time), whereas in podwall and leaf, the label initially appeared in 3-PGA. With time, the label moved to sucrose. In contrast to legumes, Brassica pods were able to fix net CO(2) during light. However, respiratory losses were very high during the dark period.
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PMID:Photosynthetic Carbon Fixation Characteristics of Fruiting Structures of Brassica campestris L. 1666 21


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