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)

After protection of cysteine-45 and -82 with iodoacetamide or N-ethylmaleimide, and in the presence of saturating concentrations of substrates, the supernatant isozyme of pig heart aspartate transaminase has been covalently modified at cysteine-390 with 3-bromo-1,1,1-trifluoropropanone. The modified enzyme retains 60-70% of the initial specific activity and is similar to native enzyme in pH and temperature stability. After tagging cysteine-390 with the fluorinated compound, the enzyme retains substrate and inhibitor binding abilities; as shown by direct spectrophotometric titration of the active-site chromophores. The 19F NMR spectrum of the modified enzyme has been obtained by a Fourier transform NMR method. Although the transaminase is a dimeric enzyme, 19F bound at each subunit's cysteine-390 gives rise to only a single 19F resonance upfield from that of trifluoroacetic acid. The fact that the chemical shifts of the 19F probe differ in native and guanidine hydrochloride (Gdn-HCl) denatured enzyme is interpreted as the effect of the native protein groups on the probe. The discordance between the changes induced by varying concentrations of Gdn-HCl on the 19F resonance parameters, on the one hand, and the changes in enzyme activity and prosthetic group absorbance, on the other, suggests that, in aspartate transaminase, cysteine-390 lies in an environment dissimilar from that of the active-site components.
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PMID:Sulphydryl group modification of aspartate aminotransferase with 3-bromo-1,1,1-trifluoropropanone during catalysis. 85 50

In this investigation the steady-state kinetic parameters of the alpha subform of aspartate aminotransferase (EC 2.6.1.1) were determined in 0.2 M Tris - HCl, pH 8.0, at 25 degrees C. The kinetic parameters for both the forward and reverse reactions were determined under conditions where the enzyme is monomeric, while only the steady-state parameters associated with the forward reaction could be determined under conditions where the enzyme is dimeric enzyme decreased relative to that of monomeric enzyme, 245 versus 360 s(-1) while the Km for aspartate increased, 3.3 versus 2.6 mM. No significant change in the Michaelis constant for ketoglutarate was observed. The steady-state parameters of dimeric enzyme are slightly altered in 0.1 M Na4 P2O7, pH 8.0, the catalytic center activity and Michaelis constant for ketoglutarate being slightly larger. From the dependence of the initial velocity on enzyme concentration the dissociation constant for the monomer-dimer equilibrium is estimated to be 2 - 10(-8) M. A similar value of the dissociation constant was estimated from Sephadex gel filtration experiments.
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PMID:Effect of aggregation on the kinetic properties of aspartate aminotransferase. 119 71

A study was performed to determine whether dietary pyridoxine affects the response of rats to arsenic deprivation. A 2 x 2 x 2 factorially arranged experiment utilized groups of 6 male weanling Sprague-Dawley rats. They were fed a 14% amino acid/76% acid-washed corn diet for 10 weeks. The dietary variables were arsenic, 0 or 1 microgram/g; pyridoxine.HCl, 0 or 10 mg/kg, and L-methionine, 0 or 3 g/kg. The basal diet contained 0.24% methionine (calculated) and about 10 ng arsenic/g. Growth was reduced by arsenic, pyridoxine or methionine deprivation. Other parameters including blood indices, erythrocyte aspartate aminotransferase and the concentration of tissue iron and plasma amino acids were affected by dietary arsenic, pyridoxine, methionine or their interaction. The data demonstrate that dietary pyridoxine and arsenic interact and that the methionine status of the animal can affect this interaction.
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PMID:Effect of dietary pyridoxine on arsenic deprivation in rats. 166 17

The tryptophan-load test for vitamin B-6 nutritional status was administered to adult female Long-Evans rats fed graded levels of pyridoxine hydrochloride (PN.HCl) in two experiments, and its sensitivity to marginal vitamin B-6 intake was evaluated. In Experiment 1, rats were 4-h meal-fed an AIN-76A (20% casein) diet devoid of PN.HCl for 3 wk, then repleted (n = 12) for 6 wk with 4-h pair-fed meals of either 0.25, 0.5, 1.0 or 7.0 (control) mg PN.HCl/kg diet. In Experiment 2, rats (n = 16) were pair-fed for 10 wk either 0.0, 0.5, 1.0 or 7.0 (control) mg PN.HCl/kg diet, with 24-h access to food. Vitamin B-6 nutritional status was assessed at the end of each experiment. Except in rats fed 0 mg PN.HCl/kg diet, mean body weights were not significantly different among diet groups of either experiment. Plasma pyridoxal phosphate (PLP), pyridoxal and total vitamin B-6 concentrations, determined by HPLC, were very sensitive to gradations in dietary PN.HCl concentrations (P less than 0.05). Red blood cell endogenous and PLP-stimulated alanine and aspartate aminotransferase activity did not statistically differentiate all levels of dietary vitamin B-6, although the calculated activity coefficient for each enzyme (stimulated/endogenous activity) did. Urinary xanthurenic acid excretion following a tryptophan load [24.5 mumol (5 mg) L-tryptophan/100 g body weight, injected intraperitoneally] was significantly (P less than 0.05) elevated compared with controls only in the group fed 0 mg PN/HCl/kg diet. At the tryptophan dose used here, the tryptophan-load test was not useful in detecting marginal vitamin B-6 intake in rats.
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PMID:Insensitivity of the tryptophan-load test to marginal vitamin B-6 intake in rats. 176 28

Twenty-four hours after acute administration of cocaine HCl (25 mg/kg, i.p.) to male C57BL/6ByJ mice, there was no hepatotoxicity as measured by plasma aspartate aminotransferase (AST) activity. In contrast, daily administration of cocaine (25 mg/kg, i.p.) for 14 days induced marked hepatotoxicity, as characterized by a greater than 400% increase in plasma AST activity when assayed 24 hr after the last injection. Concomitantly, the liver had increased levels of cysteine, gamma-glutamylcysteine, glutathione, cysteinylglycine, glutamate, methionine, taurine, and aspartate. The effect appeared to be selective for compounds of the glutathione metabolic pathways, because repeated cocaine exposure did not affect other amino acids such as leucine, isoleucine, phenylalanine, serine, and valine. There was a positive correlation between the magnitude of the elevation of cysteine and the extent of liver damage. Daily cocaine administration did not affect striatal or frontal cortex glutathione. A final cocaine challenge (50 mg/kg, i.p.) did not affect either hepatic or cerebral glutathione metabolism. The increase in hepatic cysteine and glutathione upon daily cocaine administration is a potentially important compensatory mechanism against cocaine-induced hepatotoxicity.
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PMID:Differential effects of daily administration of cocaine on hepatic and cerebral glutathione in mice. 224 12

We examined 17 lots of 2-oxoglutarate (seven acid forms, three K salt forms, and seven Na salt forms), obtained from eight commercial suppliers, for suitability for measuring aspartate aminotransferase (EC 2.6.1.1) and alanine aminotransferase (EC 2.6.1.2) in human serum. Measurements of the catalytic activity concentrations of these two aminotransferases with each of these 17 preparations were not sufficiently sensitive to distinguish good from poor-quality material. Thus, we ranked these lots for purity, by specific analysis with glutamate dehydrogenase and by liquid chromatography, and determined the water content, acid content, and spectral characteristics of each. On the basis of a 2-oxoglutarate assay value by glutamate dehydrogenase of 98% or greater, we considered seven of the preparations acceptable and 10 unacceptable. The molar absorptivities (L X mol-1 X cm-1, mean +/- SD) of the seven acceptable lots in 1 mol/L HCl were: epsilon 325 nm = 9.12 +/- 0.02 (CV = 0.2%), epsilon 279 nm = 2.63 +/- 0.23 (CV = 9.9%), and epsilon 245 nm = 37.9 +/- 4.1 (CV = 10.9%). Use of these spectrophotometric limits alone unambiguously distinguished the inferior lots of 2-oxoglutarate. We urge the inclusion of detailed spectrophotometric specifications for 2-oxoglutarate in Reference Methods for aminotransferase measurements.
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PMID:Comparisons of 17 lots of 2-oxoglutarate, and specifications for use of this substrate in reference methods. 399 57

1. The effect of pH change on the reconstitution of aspartate aminotransferase (EC 2.6.1.1), i.e. the reactivation of the apoenzyme with coenzyme (pyridoxal phosphate and pyridoxamine phosphate), was studied in the pH range 4.2-8.9 by using three buffer systems at concentrations ranging from 0.025 to 0.1m. 2. Although the profile of the reconstitution rate-pH curve in the range pH5.2-6.8 (covered by sodium cacodylate-HCl buffer) reflects the influence of the H(+) concentration on the reconstitution process, the profile of the curve in the pH ranges 4.2-5.6 and 7.2-8.25 (covered respectively by sodium acetate-acetic acid and Tris-HCl buffers) appears to be influenced by the ionic strength of the buffer. 3. The reconstitution is also influenced by univalent inorganic ions such as halide ions and, to a lesser extent, alkali metal ions, which are known to alter the water structure.
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PMID:Effect of pH, ionic strength and univalent inorganic ions on the reconstitution of aspartate aminotransferase. 485 93

The pyridoxamine (PM), pyridoxal (PL) and pyridoxol (PN) in liver, the urinary excretion of 4-pyridoxic acid (4-PA), the red blood cells enzymatic activities (aspartate aminotransferase, GOT and alanine aminotransferase, GPT) were determined in rats fed diets containing different levels of PN, HCl (0,23-170 micrograms/rat/d) during 13 days. PL and PM hepatic levels, GOT and GPT activities decreased significantly in groups A and B receiving respectively 0,23 and 11 micrograms PN, HCl/rat/d. No differences were noticed in food intake and growth. The urinary excretion of 4-PA shows a consistent trend with vitamin B6 intake. As the PM/PL-ratio was maximum in group A, PL reflects the actually available vitamer, whereas PM should be regarded as "trapped" PL. The GOT and GPT activities can be considered as reliable parameters of the pyridoxine status of the rat.
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PMID:[Effect of a controlled regimen of pyridoxol hydrochloride on the liver content of vitamin B6 and on the transaminase activities of erythrocytes in rats]. 623 77

Twelve recurrent stone formers with hyperoxaluria were administered pyridoxine-HCl (10 mg/day) daily for a period of 180 days. The pyridoxine status of the patients, as assessed by their erythrocyte transaminase activation indexes, improved significantly (p less than 0.001) after 180 days of supplementation as compared with the basal levels. Although urinary oxalate decreased significantly (p less than 0.05) by the 90th day of pyridoxine therapy, other parameters, e.g., urinary calcium, phosphorus, and creatinine, remained unaltered. Significant correlation was observed between erythrocyte glutamate pyruvate transaminase (EGPT) or erythrocyte glutamate oxaloacetate transaminase (EGOT) activation index and urinary oxalate excretion (p less than 0.01). Pyridoxine in low doses (10 mg/day) is of therapeutic value for hyperoxaluric stone formers.
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PMID:Effect of pyridoxine supplementation on recurrent stone formers. 714 62

To purify cytoplasmic and mitochondrial isoenzymes of aspartate aminotransferase (EC 2.6.1.1) from human liver. We used heat treatment, ammonium sulfate precipitation, anion- and cation-exchange chromatography, affinity chromatography, and isoelectric focusing. Final preparations of the isoenzymes were homogeneous, with specific activities of 198 and 208 kU/g for the cytoplasmic and the mitochondrial enzymes, respectively. The mitochondrial isoenzyme focused as a single band with a pl value of 9.60, whereas the cytoplasmic isoenzyme had subforms with pl values of 5.22, 5.42, and 5.62 at 4 degrees C. In Tris . HCl buffer, both isoenzymes have an activity maximum at pH 7.8. In [bis(2-hydroxyethyl)amino]tris(hydroxymethyl)methane (Bistris) buffer, however, the mitochondrial isoenzyme also showed an optimum pH of 6.7.
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PMID:Isolation and purification of aspartate aminotransferase isoenzymes from human liver by chromatography and isoelectric focusing. 746 Feb 73


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