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)

Photooxidation of a histidine residue in aspartate transaminase leads to proportionate loss of the enzyme activity in reactions with L-aspartate and L-phenylalanine. Modification of two arginine residues by 1,2-cyclohexanedione strongly inhibits transamination of aspartate but, in contrast, slightly increases the rate of phenylalanine transamination. A stimulatory effect of a number of aromatic and aliphatic monocarboxylate anions on the rate of alanine transamination in the active site was observed. Indolylbutyrate was the most effective compound among those tested. Indolylbutyrate and indolylacetate act as competitive inhibitors in the case of transamination of phenylalanine or aspartate. The results were interpreted as indicating the presence in the active center of transaminase of a hydrophobic subsite participating in the binding of aromatic aminoacids.
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PMID:[Effect of chemical modification and carboxylate anions on transamination of phenylalanine and alanine in the active center of chicken cytosol aspartate transaminase]. 56 50

Chronically alcoholized intoxication (1.5--2 months) induces adaptation of cerebral neurones to changing equilibrium states of biochemical processes by altering the activity of enzymes of GABA metabolism, reduction of alanine and aspartate transaminase activity and increase of LDH and succinate dehydrogenase activity. In the cerebellum and cerebral hemispheres during alcohol abstinacy the activity of GABA-T, succinate dehydrogenase and aspartate transaminase was reduced while that of LDH and alanine transaminase was increased. The administration of fusarinic acid (100 mg/kg i. p.) to control animals induced a sharp increase of GAD activity in both structures of the brain. The stimulatory effects of fusarinic acid were not observed when it was administered to animals receiving alcohol chronically. Motor activity or rats was markedly reduced during chronical alcoholism and the first days of alcohol abstinacy (24--48 h), as well as following injection fusarinic acid and homopantothenic acid. The increase of locomotion and the vertical component of motor activity was observed only following one week or one month after alcohol abstinacy.
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PMID:[Adaptive changes in brain metabolism during chronic alcoholic intoxication]. 57 38

Aspartate transaminase from chicken heart cytosol was immobilized covalently on activated thiol-Sepharose and digested with trypsin. After washing, the thiol-containing peptides were eluted with 2-mercaptoethanol and further purified by gel-filtration and paper chromatography. Three pure cysteinyl peptides were isolated. One of them may be represented as Ile-(Asp, Met, Cys, Gly, Leu, Thr2)-Lys; this peptide is identical to the fragment comprizing residues 387--395 in the peptide chain of aspartate transaminase from pig heart cytosol. It thus contains a cysteine residue homologous to Cys-390 of the pig heart enzyme. The second cysteinyl peptide had the following composition and partial sequence: Tyr-Phe-Val-Ser-Glu-Gly-Phe-Glu-Leu-Phe (Cys, Ala, Glu, Ser2, Phe)Lys, which corresponds to the sequence 242--258 of the pig enzyme and thus contains a cysteine residue homologous to Cys-252. The third cysteinyl peptide was similar to the tryptic peptide of the pig enzyme containing Cys-191.
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PMID:[Thiol peptides from the aspartate transaminase of chicken heart cytosol]. 59 23

Reaction of 1,2-cyclohexanedione with chicken heart cytosolic aspartate transaminase results in loss of enzyme activity complying to first order kinetics up to 70% inactivation. The inactivation rate is markedly decreased in the presence of alpha-ketoglutarate, glutarate or alpha-methylaspartate. The number of arginine residues modified per subunit was approximately two (in enzyme preparations which retained 30% residual activity). The diketone-modified enzyme nearly completely loses affinity for alpha-methylaspartate and glutarate; in contrast, its ability to bind alpha-alanine and catalyze its transamination half-reaction with the bound coenzyme remains unimpaired. From these data it can be inferred that a functional arginine residue is the cationic binding site for the distal carboxyl group of the substrates. The transaminase apoenzyme was inactivated with cyclohexanedione at the same rate as reconstituted holoenzyme. Measurements of circular dichroism showed that the modified apoenzyme is capable to bind pyridoxal-P. No evidence was obtained for the presence of an arginine residue in the coenzyme binding site.
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PMID:[Study of the role of arginine residues in aspartate transaminase from chicken heart cytosol]. 65 97

In isolated hepatocytes from normal fed rats, the subcellular distribution of malate, citrate, 2-oxoglutarate, glutamate, aspartate, oxaloacetate, acetyl-CoA and CoASH has been determined by a modified digitonin method. Incubation with various substrates (lactate, pyruvate, alanine, oleate, oleate plus lactate, ethanol and aspartate) markedly changed the total cellular amounts of metabolites, but their distribution between the cytosolic and mitochondrial compartments was kept fairly constant. In the presence of lactate, pyruvate or alanine, about 90% of cellular aspartate, malate and oxaloacetate, and 50% of citrate was located in the cytosol. The changes in acetyl-CoA in the cytosol were opposite to those in the mitochondrial space, the sum of both remaining nearly constant. The mitochondrial acetyl-CoA/CoASH ratio ranged from 0.3-0.9 and was positively correlated with the rate of ketone body formation. The mitochondrial/cytosolic (m/c) concentration gradients for malate, citrate, 2-oxoglutarate, glutamate, aspartate, oxaloacetate, acetyl-CoA and CoASH averaged from hepatocytes under different substrate conditions were determined to be 1.0, 8.8, 1.6, 2.2, 0.5, 0.7, 13 and 40, respectively. From the distribution of citrate, a pH difference of 0.3 across the inner mitochondrial membrane was calculated, yet lower values resulted from the m/c gradients of 2-oxoglutarate, glutamate and malate. The mass action ratios for citrate synthase and mitochondrial aspartate aminotransferase have been calculated from the metabolite concentrations measured in the mitochondrial pellet fraction. A comparison with the respective equilibrium constants indicates that in intact hepatocytes, neither enzyme maintains its reactants at equilibrium. On the assumption that mitochondrial malate dehydrogenase and 3-hydroxybutyrate dehydrogenase operate near equilibrium, the concentration of free oxaloacetate appears to be 0.3-2 micron, depending on the substrate used. Plotting the calculated free mitochondrial oxaloacetate concentration against the citrate concentration measured in the mitochondrial pellet yielded a hyperbolic saturation curve, from which an apparent Km of citrate synthase for oxaloacetate in the intact cells of 2 micron can be derived, which is comparable to the value determined with purified rat liver citrate synthase. The results are discussed with respect to the supply of substrates and effectors of anion carriers and of key enzymes of the tricarboxylic acid cycle and fatty acid biosynthesis.
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PMID:Distribution of metabolites between the cytosolic and mitochondrial compartments of hepatocytes isolated from fed rats. 68 Jun 39

Activity of alanine and aspartate aminotransferase, alkaline phosphatase, adenosine, desaminase and AMP-aminohydrolase was determined in rats in the process of the liver regeneration under acute and chronic lesion with CCl4. It is shown that under chronic lesion of the liver with CCl4, in contrast to the acute one, changes in the aminotransferase activity in blood serum are not expressed in the liver, the activity is essentially decreased. A steady increase was observed in the activity of adenosine desaminase, AMP-aminohydrolase and alkaline phosphatase in the liver and blood serum. It is concluded that the normal regenerative process is accompanied by short-term shifts of the enzymes activity in the liver and blood serum. The development of a chronic process results in a characteristic increase in the activity of adenosine desaminase, AMP-aminohydrolase and alkaline phosphatase in the liver and blood serum.
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PMID:[Enzyme activity during regeneration under acute and chronic liver lesion with CCL4]. 68 74

1. Diets containing graded levels of pyridoxine hydrochloride (to supply 0.26--30 mg pyridoxine/kg) were given to seven duplicate groups of turbot (Scophthalmus maximus) for 12 weeks and their growth rate was measured during this period. 2. Good growth was obtained on all treatments except those groups given less than 1.0 mg pyridoxine/kg diet. These fish grew normally until weeks 8--10 but thereafter their weight gain was significantly less than that for other treatments. 3. Measurements of aspartate aminotransferase (EC 2.6.1.1) in muscle and liver and of alanine amino-transferase (EC 2.6.1.2) in liver of the turbot showed that the activities of these enzymes increased with increasing dietary pyridoxine intake up to a level of 2.5 mg pyridoxine/kg. The activities of these enzymes were not further enhanced by additional dietary pyridoxine. 4. Percentage stimulation of these enzymes by pre-incubation of extracts with pyridoxal phosphate was minimal with those groups of turbot given 2.5 mg pyridoxine/kg diet or more. 5. It is concluded that the dietary requirement of turbot for vitamin B6 can be safely met with a diet containing between 1.0 and 2.5 mg pyridoxine/kg. 6. An eighth group of turbot given the pyridoxine antagonist 4-deoxypyridoxine hydrochloride (20 mg/kg) showed retarded growth after 2 weeks, together with a high mortality rate.
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PMID:Studies on the nutrition of marine flatfish. The pyridoxine requirement of turbot (Scophthalmus maximus). 69 64

Glutamate-auxotrophic mutants lacking phosphoenolpyruvate carboxylase(PC), citrate synthase (CS) or glutamate dehydrogenase (GD), an aspartate auxotroph lacking aspartate aminotransferase (TA), and a glutamate-aspartate double auxotroph lacking both aconitase (AH) and TA were obtained from Brevibacterium flavum No. 2247, a glutamate-producing bacterium. Prototrophic revertants further derived from the CS- and GD-lacking auxotrophs concomitantly recovered the enzyme activities that their parents had lost. These results indicate involvement of the tricarboxylic acid (TCA) cycle and GD in glutamate biosynthesis, that of PC in the biosynthesis of the TCA cycle intermediates and that of TA in aspartate biosynthesis. The CS-deficient mutants accumulated large amounts of acetate and small amounts of pyruvate, aspartate and alanine, while the GD-deficient strains accumulated large amounts of 2-oxo-glutarate and small amounts of citrate. Synthesis of PC was repressed by either glutamate or aspartate and those of CS and GD were repressed by glutamate, whereas those of pyruvate dehydrogenase (PD), AH, and isocitrate dehydrogenase were not affected significantly by glutamate; that of TA was also not affected by aspartate or by glutamate. The specific activities of PD and AH gave peaks during the cellular cultivation, related to the temporary accumulation of their substrates, pyruvate and citrate, respectively. These and previous results on the regulation of the enzymatic activities provide a definite regulatory mechanism for glutamate and aspartate syntheses.
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PMID:Enzymes of the glutamate and aspartate synthetic pathways in a glutamate-producing bacterium, Brevibacterium flavum. 72 99

Cysteine aminotransferase has been purified over 300-fold from rat liver mitochondria. Transamination between L-cysteine and 2-oxoglutarate, and the reverse reaction, were observed to be catalyzed by the purified enzyme but inhibited by L-aspartate. The enzyme also catalyzed transamination of alanine, 3-sulfinic acid, aspartic acid, and cysteic acid. A new reaction assay method was devised, contributing an indication that mitochondrial cysteine aminotransferase is identical to mitochondrial aspartate aminotransferase. The latter apparently catalyzed 3 transamination reactions in the cysteine degradation process within mitochondria.
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PMID:Purification and characterization of mitochondrial cysteine aminotransferase from rat liver. 75 89

To investigate the activation of aspartate- and alanine aminotransferases by pyridoxal-5'-phosphate, we determined the enzymatic activity in serum in two different ways: (a) Preincubation of the serum alone or the serum with pyridoxal-5'-phosphate and starting the reaction by the addition of the serum sample or the serum sample + coenzyme, respectively. (b) Preincubation of the serum or the serum with pyridoxal-5'-phosphate in the reaction medium and starting the reaction by adding 2-oxoglutarate. There are only small differences in activities of both aminotransferases determined according to these two different methods. The stimulation by pyridoxal-5'-phosphate is also of the same order, when both methods are compared. Further, these enzymatic activities were measured with use of various concentrations of substrates. From our experiments we conclude that the degree of stimulation of the apoenzyme of the two enzymes is independent of which way the enzymatic reaction is carried out or the substrate concentration, except that aspartate aminotransferase activity is more stimulated by the coenzyme at higher 2-oxoglutarate concentrations.
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PMID:Determination of serum aminotransferases: activation by pyridoxal-5'-phosphate in relation to substrate concentration. 76 81


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