Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.6.1.2 (alanine aminotransferase)
 26,722 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cerebral metabolic effects of 2.5, 5, 7.5, 10, 20, 30 and 60 min exposure to 1% CO were studied in lightly anesthetized rats by measurement of cerebral cortical contents of selected glycolytic and citric acid cylce intermediates, as well as tissue energy phosphates. The initial change in the glycolytic sequence occurred at 2.5 min with decreases in tissue glucose and glucose-6-phosphate and increases in fructose-1-6-diphosphate which indicated an activation of phosphofructokinase and hexokinase. The "crossover" pattern between glucose-6-phosphate and fructose-1,6-diphosphate was present at 5, 7.5 and 10 min, but not at 20, 30 and 60 min and thus confirmed previous observations that detection of phosphofructokinase activation in acute unifactorial cerebral hypoxia requires tissue study during the early phases of the experimental exposure. The initial activation of phosphofructokinase occurred in the absence of detectable changes in the tissue content of ATP, ADP, AMP or phosphocreatine and therefore suggested that an imbalance of tissue energy homeostasis is not a prerequisite for the activation of glycolysis in CO intoxication. One percent CO resulted in an increasing malate/oxaloacetate ratio at 5 min, followed by a decrease in alpha-ketoglutarate and aspartate at 7.5 min which suggested a shift in the aspartate aminotransferase reaction towards the replenishment of oxaloacetate removed via the malate dehydrogenase reaction. Subsequent increases in alpha-ketoglutarate at 10, 20, 30 and 60 min were associated with increases in alanine, indicating a contributing role for a secondary shift of the alanine aminotransferase reaction in the replenishment of alpha-ketoglutarate. A comparison of the CO induced changes in the glycolytic and citric acid cycle pathways with those seen in acute hypoxemia indicates no basic qualitative differences in the metabolic responses of brain tissue to the two conditions.
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PMID:Cerebral carbohydrate metabolism during acute carbon monoxide intoxication. 1 62

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

Subcellular distribution and some physicochemical properties of alanine aminotransferase in striated muscles of the crayfish, trout, carp, frog, pigeon and rabbit were studied. It was established that: (1) Alanine aminotransferase activity in all mentioned animals occurred almost entirely in the cytosolic fraction of the muscles. Total activity and activity per mg protein were highest in crayfish and pigeon muscles and lowest in carp and trout muscles. (2) The pH optimum for the muscles of homoiotherms and poikilotherms ranged from 7.5 to 8, Km values for L-alanine were of the order 10(-3)--10(-2) M and those for alpha-ketoglutarate 10(-4) M. (3) A 10 degree C temperature increase of the incubation medium was accompanied by a 70--90% increase in activity. (4) The higher the alanine aminotransferase activity of the muscles, the relatively higher their alanine production during electrical stimulation. (5) From the above results it is concluded that alanine aminotransferase in striated muscles regulates the rate of glycolysis and energy production under conditions of anaerobiosis through the formation of alanine.
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PMID:Subcellular distribution and some properties of alanine aminotransferase in striated muscles of the crayfish, trout, carp, frog, pigeon and rabbit. 3 68

Treatment of male guinea-pigs daily with an oral dose of 2 mg dehydroepiandrosterone (DHA) sulphate/100 g body weight for 2 weeks significantly reduced the glucose-6-phosphate dehydrogenase (G-6-PDH) activity of erythrocytes, liver, kidney and testis. Lactate dehydrogenase activity in plasma also decreased, but L-aspartate: 2-oxoglutarate aminotransferase (GOT) and L-alanine:2-oxoglutarate aminotransferase (GPT) activity in plasma remained unaffected. In liver and kidney, however, a significant rise in GOT and GPT was observed. A 2- to 3-7-fold increase of C19-steroids was observed in plasma, liver and kidney. In extracts of liver and kidney more than 60% of steroids were isolated from the sulphatide fraction. Only minor changes were detected in the metabolic pattern of C19-steroids, 17-hydroxysteroids prevailing in the free and sulphatide fractions, while 17-oxosteroids predominated in the sulphate and glucuronide fractions. A slight rise of cyclic AMP concentrations in liver and kidney tissue was attributed to the inhibition of phosphodiesterase by the DHA/G-6-PDH system
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PMID:Effects of exogenous dehydroepiandrosterone sulphate on various enzymes and on steroid metabolism in the guinea-pig. 13 7

1. A reversible transamination reaction between L-glutamate and pyruvate, or L-alanine and 2-oxoglutarate, takes place in the mitochondrial and cell sap fractions of rat brain. 2. The maximum rate of the transamination reaction in both subfractions was observed in the presence of a keto- substrate concentration of 2.5 mM only, but an amino- donor concentration of 20 mM. 3. The apparent Menten-Michaelis constants for pyruvate and 2-oxoglutarate were of a 10(-4) M and for L-glutamate and L-alanine of a 10(-3) M order and were approximately the same for both fractions. 4. The ratio of the initial rate of the L-alanine + 2-oxoglutarate to the L-glutamate + pyruvate transamination reaction in the cell sap and mitochondrial fractions amounted to up to 2. 5. The apparent equilibrium constant derived from the Haldane equation was 7.01 for cell sap alanine aminotransferase and 4 for the mitochondrial enzyme. 6. Increasing pyridoxal-5'-phosphate concentrations in the incubation medium were accompanied by only non-significant stimulation of alanine aminotransferase activity in the mitochondrial and cell sap fractions. 7. A comparison of the kinetic data obtained on mitochondrial and cell sap alanine aminotransferases in vitro with the actual substrate concentrations in the transamination reaction in nervous tissue in vivo indicates that the direction of the transamination reaction in situ seems to be determined simply by compartmentation and by dynamic changes in amino- and keto- substrates in the mitochondrial and cell sap spaces.
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PMID:Kinetics of the alanine aminotransferase reaction in the mitochondrial and cell sap fractions of rat brain. 14 Mar 99

The protective effect of pyridoxine-2-oxoglutarate (ACP) was studied on CCl4-intoxicated rats. A sensitive improvement of hepatic conditions was shown in ACP-treated rats as compared with untreated ones and rats treated with 2-oxoglutarate and pyridoxine. Serum GOT, GPT, OCT activities, composition of serum proteins, liver mitochondria respiratory control index and liver microsomes oxidizing activity were tested. The antiketotic properties of ACP were also demonstrated in Streptozotocin treated rats.
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PMID:Effect of ACP (pyridoxine-2-oxoglutarate) on CCl4 intoxication and in streptozotocin-induced ketosis in rat. 15 Jul 79

We investigated the enzyme activity of the blank in the spectrophotometric determination of the aminotransferase activities and aspartate aminotransferase activity. 6 lactate dehydrogenase and 3 malate dehydrogenase preparations from different manufactures and from different organs showed additional and contaminating activity. The additional activity depends upon the 2-oxoglutarate concentration. The contaminating activity is caused by alanine aminotransferase and aspartate aminotransferase in the auxiliary enzymes. We propose that exact definitions must be given for the auxiliary enzymes in the recommendations of standard determinations for enzyme activities.
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PMID:Influence of auxiliary enzymes on the spectrophotometric measurement of alanine aminotransferase and aspartate aminotransferase activities. 17 28

1)The time course of changes in concentration of renal metabolites in response to a non-toxic load of NH4 as NH4 Cl or NH4HCO3 were measured in fasted rats. 2) Following a NH4Cl load, decrease of renal concentration of 2-oxoglutarate occurs but this change is delayed in relation to the peak of the blood ammonia concentration and persists after disappearance of the hyperammoniemia. 3) Following a NH4HCO3 load, the oxoglutarate concentration changes are less marked and more transient. 4) No close relationship between the mitochondrial free NAD/NADH ratio calculated from the glutamate dehydrogenase and the 3-hydroxybutyrate dehydrogenase systems were seen during alteration of the ammonia concentration. 5) Contrary to the observations in the liver under similar circumstances (BROSNAN, J.T. et al.: Biochem.J. 138, 453, 1974), no increase in kidney tissue or renal venous blood alanine or aspartate concentration are seen. 6) A constant infusion of NH4HCO3 resulted only in an increase in tissue and renal venous blood glutamine concentration. 7) The infusion of NH4 together with a carbon source (malate) resulted in a similar increase in tissue glutamine concentration and more striking increase in renal venous glutamine concentration. No accumulation of aspartate nor alanine were seen. 8) In vitro studies indicate that the net flux through both the aspartate aminotransferase and the glutamate dehydrogenase reactions is dependent on the concentration of the reactants as expected for a near-equilibrium system. 9) It is concluded that the kidney response to an ammonia load differs from that of the liver despite the existence of a similar network of near-equilibrium reactions of (1) a lack of local availability of oxaloacetate, (2) a lower activity of alanine aminotransferase, (3) a greater in vivo activity of glutamine synthetase.
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PMID:Effect of an ammonia load on the kidney near-equilibrium systems in the rat in vivo. 18 80

The sequential pattern of lipid accumulation and associated biochemical changes were studied in two commonly used experimental models of nutritional fatty liver in rats. Female rats were maintained for 8 weeks on high fat, low protein diets containing adequate methionine and choline, and drinking water ad libitum (Diet 1), or deficient in methionine and choline and containing 20% ethanol as a substitute for drinking water (Diet 2). Histologically, there was a progressive increase in liver lipids, mainly in the periportal areas. Occasional foci of liver cell necrosis with lipogranuloma formation occurred in areas of severe fatty change. These changes appeared earlier and were more marked in rats maintained on Diet 2. Electron micrographs revealed large lipid droplets in the liver cells, which sometimes contained myelin figures. The mitochondria were enlarged, distorted and appeared as amorphous structures with disorientated cristae in rats on Diet 1, whereas they had a condensed conformation in rats maintained on Diet 2. Rough endoplasmic reticulum was fragmented and degranulated particularly in rats on Diet 1, and smooth endoplasmic reticulum showed hyperplasia and vesiculation in rats on Diet 2. There was a progressive increase in the total liver lipids and triglycerides in both the groups of rats. This fatty change was accompanied by a significant increase in hepatic 3-hydroxybutyrate, acetoacetate, malate, 2-oxoglutarate, citrate, lactate, ammonia, glutamate, alanine and aspartate, and a significant decrease in oxaloacetate, urea and glucose concentrations. The mass action ratios for alanine aminotransferase, aspartate amino transferase, and glutamate dehydrogenase, generally moved in a parallel direction. Hepatic ATP content was considerably reduced accompanied by a decrease in [ATP]/[ADP] ratios and a significant increased in [lactate]/[pyruvate] and [3-hydroxybutyrate]/[acetoacetate] ratios. There was a corresponding decrease in the [NAD+]/[NADH] ratios both in the cytoplasmic and mitochondrial compartments. These biochemical changes were particularly severe in rats maintained on Diet 1 and Diet 2 for 8 weeks. There was a very good relationship between impaired mitochondrial and endoplasmic reticulum functions, redox and phosphorylation states, and the relevance of their changes to the fate of fatty liver cells.
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PMID:Lipid accumulation in the rat liver: a histological and biochemical study. 23

Kynurenine transaminase activity in rat kidney was found in both the mitochondrial and supernatant fractions. These fractions contained (a) kynurenine pyruvate transaminase, which showed a preference for pyruvate as amino acceptor, and had a pH optimum between 8.0 and 8.5, and (b) kynurenine 2-oxoglutarate transaminase, with a preference for 2-oxoglutarate and a pH optimum between 6.0 and 6.5. The apparent Km value of the former enzyme for L-kynurenine was much lower than that of the latter enzyme.
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PMID:Subcellular distribution and properties of kynurenine pyruvate transaminase in rat kidney. 24 Jul 68


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