Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P17174 (aspartate aminotransferase)
 14,872 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
 ...
PMID:Enzymes of the glutamate and aspartate synthetic pathways in a glutamate-producing bacterium, Brevibacterium flavum. 72 99

In addition to the normal carboxylation reaction, phosphoenolpyruvate carboxylase from Zea mays catalyzes a HCO3(-)-dependent hydrolysis of phosphoenolpyruvate to pyruvate and Pi. Two independent methods were used to establish this reaction. First, the formation of pyruvate was coupled to lactate dehydrogenase in assay solutions containing high concentrations of L-glutamate and aspartate aminotransferase. Under these conditions, oxalacetic acid produced in the carboxylation reaction was efficiently transaminated, and decarboxylation to form spurious pyruvate was negligible. Second, sequential reduction of oxalacetate and pyruvate was achieved by initially running the reaction in the presence of malate dehydrogenase with NADH in excess over phosphoenolpyruvate. After the reaction was complete, lactate dehydrogenase was added, thus giving a measure of pyruvate concentration. At pH 8.0 in the presence of Mg2+, the rate of phosphoenolpyruvate hydrolysis was 3-7% of the total reaction rate. The hydrolysis reaction catalyzed by phosphoenolpyruvate carboxylase was strongly metal dependent, with rates decreasing in the order Ni2+ greater than Co2+ greater than Mn2+ greater than Mg2+ greater than Ca2+. These results suggest that the active site metal ion binds to the enolate oxygen, thus stabilizing the proposed enolate intermediate. The more stable the enolate, the less reactive it is toward carboxylation and the greater the opportunity for hydrolysis.
 ...
PMID:Hydrolysis of phosphoenolpyruvate catalyzed by phosphoenolpyruvate carboxylase from Zea mays. 163 56

The mechanism of C4 acid decarboxylation was studied in bundle sheath cell strands from Urochloa panicoides, a phosphoenolpyruvate carboxykinase (PCK)-type C4 plant. Added malate was decarboxylated to give pyruvate and this activity was often increased by adding ADP. Added oxaloacetate or aspartate plus 2-oxoglutarate (which produce oxaloacetate via aspartate aminotransferase) gave little metabolic decarboxylation alone but with added ATP there was a rapid production of PEP. For this activity ADP could replace ATP but only when added in combination with malate. In addition, the inclusion of aspartate plus 2-oxoglutarate with malate plus ADP often increased the rate of pyruvate production from malate by more than twofold. Experiments with respiratory chain inhibitors showed that the malate-dependent stimulation of oxaloacetate decarboxylation (PEP production) was probably due to ATP generated during the oxidation of malate in mitochondria. We could provide no evidence that photophosphorylation could serve as an alternative source of ATP for the PEP carboxykinase reaction. We concluded that both PEP carboxykinase and mitochondrial NAD-malic enzyme contribute to C4 acid decarboxylation in these cells, with the required ATP being derived from oxidation-linked phosphorylation in mitochondria.
 ...
PMID:Photosynthesis in phosphoenolpyruvate carboxykinase-type C4 plants: pathways of C4 acid decarboxylation in bundle sheath cells of Urochloa panicoides. 334 40

1. The activities of gluconeogenic and glycolytic enzymes and the concentrations of citrate, ammonia, amino acids, glycogen, glucose 6-phosphate, acetyl-CoA, lactate and pyruvate were measured in kidney cortex of normal, diabetic, cortisone-treated and growth hormone-treated rats. 2. In kidney cortex of diabetic, cortisone-treated and growth hormone-treated rats the activities of glucose 6-phosphatase (EC 3.1.3.9), fructose 1,6-diphosphatase (EC 3.1.3.11) and phosphopyruvate carboxylase (EC 4.1.1.32) were increased. 3. The activities of glutamate dehydrogenase (EC 1.4.1.3), alanine aminotransferase (EC 2.6.1.2), aspartate aminotransferase (EC 2.6.1.10) and pyruvate carboxylase (EC 6.4.1.1) were increased in diabetic and cortisone-treated rats. In growth hormone-treated rats the activity of aspartate aminotransferase was depressed but those of the other three enzymes were unchanged. 4. The activity of hexokinase (EC 2.7.1.1) was not altered in any of these conditions. Phosphofructokinase (EC 2.7.1.11) activity was depressed only in growth hormone-treated rats. Pyruvate kinase (EC 2.7.1.40) activity was depressed in cortisone-treated and growth hormone-treated rats but unchanged in diabetic rats. 5. Amino acids, acetyl-CoA and glucose 6-phosphate contents were increased in rat kidneys in all these three conditions. Ammonia content was increased in diabetic and cortisone-treated rats but was markedly diminished in growth hormone-treated rats. 6. The [lactate]/[pyruvate] ratio was elevated in diabetic and cortisone-treated rats but unchanged in growth hormone-treated rats. Citrate content was increased in the kidney cortex of diabetic and growth hormone-treated rats but was unchanged in cortisone-treated rats. The activity of ATP citrate lyase (EC 4.1.3.8) was depressed in diabetic and growth hormone-treated rats but was increased in cortisone-treated rats. 7. Glycogen content was moderately elevated in growth hormone-treated rats and markedly elevated in diabetic rats, whereas no change in glycogen content was observed in cortisone-treated rats. Glycogen synthetase (EC 2.4.1.11) activity was unchanged in all these three conditions. Phosphorylase (EC 2.4.1.1) activity was not affected in cortisone-treated rats but was depressed in diabetic and growth hormone-treated rats.
 ...
PMID:Evaluation of the rate-limiting steps in the pathway of glucose metabolism in kidney cortex of normal, diabetic, cortisone-treated and growth hormone-treated rats. 434 56

1. The hepatic concentrations of the ketone bodies and of metabolites and activities of enzymes involved in gluconeogenesis were measured in healthy lactating and non-lactating cows 48h after administration of Voren, an ester of dexamethasone, and compared with those found in control animals given saline. Parallel measurements were also made of the blood concentrations of several of the metabolites. 2. Blood glucose concentrations were raised in the Voren-treated animals, whereas blood ketone body and free fatty acid concentrations were unaltered. Similarly there was no change in the hepatic concentrations of the ketone bodies. 3. Significant increases were found in the hepatic concentrations of citrate, 2-oxo-glutarate and malate in both groups of animals given Voren. 4. The hepatic concentrations of those glycolytic intermediates that were measured either decreased or did not change after Voren treatment. 5. The enzymes aspartate transaminase and fructose 1,6-diphosphatase were unchanged in activity after Voren administration, whereas phosphopyruvate carboxylase (EC 4.1.1.32) activity was depressed in the lactating group. However, glucose 6-phosphatase, tryptophan oxygenase and tyrosine aminotransferase increased in activity. 6. In several cases those hepatic metabolites that increased in concentration after Voren administration were present in lower concentration in normal lactating cows than in normal non-lactating cows. The same applied mutatis mutandis to those metabolites that were decreased by Voren. 7. These findings are discussed in relation to the use of glucocorticoids in the treatment of bovine ketosis.
 ...
PMID:Gluconeogenesis in the cow. The effects of a glucocorticoid on hepatic intermediary metabolism. 439 35

1. In confirmation of previous work, administration of d(+)-galactosamine (0.5-0.75g/kg body wt.) to rats caused a hepatitis with histological evidence of liver damage and a 9-fold rise in aspartate aminotransferase activity in serum. 2. There was a significant elevation of blood lactate and pyruvate concentrations in 24h-starved rats treated with galactosamine but no change in the [lactate]/[pyruvate] ratio. 3-Hydroxybutyrate and acetoacetate concentrations in blood were decreased. 3. The changes in the concentrations of lactate, pyruvate and ketone bodies in the freeze-clamped liver were parallel to those observed in the blood. 4. In the livers of 24h-starved galactosamine-treated rats there were large increases in the concentrations of alanine (3-fold), citrate (5-fold), 2-oxoglutarate (4-fold), with smaller increases in malate, glutamate and aspartate. There was a 4-fold rise in the value of the mass-action ratio of the alanine aminotransferase system in the livers of galactosamine-treated rats when compared to controls. 5. There was a significant decrease in the activities of aspartate and alanine aminotransferases in the cytoplasm and the soluble fraction of sonicated homogenates of the livers of rats treated with galactosamine. The activity of phosphoenolpyruvate carboxylase was decreased by 75% of the control value. 6. Glucose synthesis from lactate in perfused livers from galactosamine-treated rats was inhibited 39% when compared with controls. 7. The results indicate that the conversion of lactate into glucose is decreased in the livers of galactosamine-treated rats and that this decrease may be due to the loss of phosphoenolpyruvate carboxylase from damaged hepatocytes.
 ...
PMID:Metabolic studies in experimental liver disease resulting from D(+)-galactosamine administration. 465 44

14C-labeled bicarbonate was incorporated into trichloroacetic acid-insoluble material by cell suspensions of A. viscosus strain M100 and also into the four-carbon fermentation product, succinate, but not into the three-carbon fermentation product, lactate. The initial step in the conversion of 14C-labeled bicarbonate into both trichloroacetic acid-insoluble material and succinate was catalyzed by the enzyme phosphoenolypyruvate carboxylase, which served to convert the glycolytic intermediate, phosphoenolpyruvate, and bicarbonate to the four-carbon compound, oxalacetate. The metabolic fate of oxalacetate was its conversion to either trichloroacetic acid-insoluble material or succinate. One pathway by which oxalacetate may be metabolized into acid-insoluble material is via its conversion to the biosynthetic precursor aspartate by the action of glutamate aspartate aminotransferase. One source of the alpha-amino group of aspartate was the ammonium ion, which could be incorporated into glutamate, the substrate of the glutamate aspartate aminotransferase reaction, by the action of a reduced nicotinamide adenine dinucleotide phosphate-dependent glutamate dehydrogenase whose reducing equivalents could be derived from the nicotinamide adenine dinucleotide phosphate-dependent oxidative reactions of the hexose monophosphate pathway catalyzed by glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Alternatively, oxalacetate was converted to the fermentation product, succinate, through the sequential action of malate dehydrogenase, fumarase, and succinic dehydrogenase. The resolution and partial purification of phosphoenolpyruvate carboxylase, glutamate aspartate aminotransferase, glutamate dehydrogenase, malate dehydrogenase, fumarase, and succinic dehydrogenase are also reported.
 ...
PMID:Carbon dioxide metabolism by Actinomyces viscosus: pathways for succinate and aspartate production. 676 22

The activity of enzymes with a regulatory function in the pathways of glycolysis, glyconeogenesis and NADP-generation, and the tissue content of DNA, protein, glycogen, triglycerides (TG), phospholipids (PL), cholesterol and dry matter were investigated in placentas from deliveries accompanied by fetal distress as a result of umbilical cord compression or placental dysfunction in toxemic pregnancies. In placentas from cases of fetal distress due to umbilical cord compression, there was increased activity of pyruvate kinase, 6-phosphogluconate dehydrogenase and NADP-malate dehydrogenase, and decreased activity of phosphoenolpyruvate carboxylase. The activity of aspartate aminotransferase was unchanged, and that of glucose-6-phosphate dehydrogenase was slightly elevated. The tissue content of dry matter, DNA, TG and PL was increased, whereas the protein, cholesterol and glycogen concentrations remained unaltered. In placentas from deliveries accompanied by fetal distress due to placental dysfunction, pyruvate kinase, when calculated per mg protein, was the only enzyme with decreased activity. TG, PL, glycogen and dry matter content were increased, DNA concentration was decreased, and protein and cholesterol remained unchanged. It is suggested that the divergent placental metabolic patterns found in the two fetal distress groups are related to the different levels of disturbed oxygen passage along the uterus-placenta-fetus axis.
 ...
PMID:The placenta in intrauterine fetal deprivation. II. Biochemical profile of placentas from deliveries associated with fetal distress. 735 17

Panicum miliaceum has at least three isozymes of aspartate aminotransferase (AspAT); the cytosolic and mitochondrial isozymes (cAspAT and mAspAT) are major components and the third is a minor isozyme. Fractionation of leaf subcellular components showed that the minor isozyme was localized in plastids (pAspAT). We purified the three isozymes from green leaves of P. miliaceum. Both cAspAT and pAspAT consisted of triple subforms having the same molecular size but different isoelectric points. No substantial difference in enzymatic properties was observed among these isozymes besides the pH profiles. We isolated a full-length cDNA clone for pAspAT. This clone contains an open reading frame that encodes 457 amino acids. The amino-terminal region of the pAspAT precursor shares common features of plastid transit peptides. The amino acid sequence of P. miliaceum pAspAT shows higher similarity with other plant pAspATs than P. miliaceum cAspAT and mAspAT. The mRNA levels of the three isozymes were high in leaves compared with roots and mesocotyls. The three isozymes showed different expression patterns against environmental stimuli such as light and nitrate. The activities and protein levels of cAspAT and mAspAT increased during greening in accordance with those of phosphoenolpyruvate carboxylase and NAD-malic enzyme involved in the C4 pathway, primarily as a consequence of the increase in the levels of their mRNAs. By contrast, pAspAT was constitutively expressed during greening. The activity and protein levels of cAspAT and mAspAT selectively increased during recovery from an nitrogen deficit, primarily as a consequence of increase in the levels of their mRNAs while those of pAspAT remained unchanged.
 ...
PMID:Aspartate aminotransferase isozymes in Panicum miliaceum L., an NAD-malic enzyme-type C4 plant: comparison of enzymatic properties primary structures, and expression patterns. 773 57

The aim of this study was to evaluate the biochemical events in root nodules which lead to increased yield when bean is inoculated with a Rhizobium etli mutant (CFN037) having increased respiratory capacity. CFN037-inoculated plants had 22% more nitrogen (N) than did wild-type (CE3)-inoculated plants. Root nodule enzymes involved in nodule carbon and nitrogen assimilation as well as in ureides and amides synthesis were assessed in plants inoculated with CFN037 and the CE3. Our results show that the xylem ureides content was lower while that of amino acids was higher in CFN037- compared with CE3-inoculated plants. Supporting these results, enzymes involved in ureide synthesis were reduced while activity of aspartate aminotransferase, glutamate synthase, sucrose synthase, and glucose-6-P dehydrogenase were increased in CFN037-induced nodules. Glutamate synthase and phosphoenolpyruvate carboxylase transcripts were detected early in the development of nodules induced by CFN037 compared with CE3. However, plants inoculated with strain CE3-vhb, which express the Vitreoscilla sp. hemoglobin and also displays increased respiratory capacity, did not have altered ureide transport in N2-fixing plants. The data suggest that inoculation with special selected mutant strains of R. etli can modulate nodule N assimilation and N transport compounds.
 ...
PMID:Rhizobium etli mutant modulates carbon and nitrogen metabolism in Phaseolus vulgaris nodules. 1211 89


1 2 3 Next >>