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)

Two isoenzymic forms of aspartate aminotransferase are present in the plant fraction of developing lupin root nodules. One of these forms, aspartate aminotransferase-P2 (AAT-P2), increases dramatically with the onset of biological nitrogen fixation and is associated with the assimilation of ammonia by the plant in the Rhizobium-legume symbiosis. A day 18 lupin nodule cDNA library in the lambda ZapII vector was immunoscreened with a monoclonal antibody specific for AAT-P2 and yielded two near-full-length 1700 bp clones. These clones were sequenced. Amino acid sequences from three peptides derived from immunopurified AAT-P2 were aligned, and showed 100% homology with the amino acid sequence deduced from the cDNA clones. The DNA sequence showed 50% homology with AAT sequences from a range of animal sources. Conversion of the clones to the phagemid form allowed their expression in Escherichia coli where both exhibited enzyme activity that could be immunoprecipitated with AAT-P2-specific monoclonal antibodies. Western blot analysis revealed protein moieties with molecular masses of 39, 43, 45 and 55 kDa. The 5' end of the clones coded for a hydrophobic leader sequence of about 50 amino acids indicative of a targeting sequence and consistent with the plastid localisation of nodule AAT-P2.
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PMID:Molecular cloning of a cDNA encoding aspartate aminotransferase-P2 from lupin root nodules. 162 92

Observation of the 93-kDa cytosolic aspartate aminotransferase by 500-MHz 1H NMR spectroscopy in H2O has revealed a series of resonances in the 10-18 ppm range arising from exchangeable protons. One of these (peak A) has been assigned to the proton bound to the ring nitrogen of the coenzyme pyridoxal 5'-phosphate. A second (peak B) is assigned to H143 which participates in a chain of hydrogen bonds that includes also the coenzyme-bound proton. There is a mutual nuclear Overhauser effect between these two resonances. Peaks A and B respond to changes in pH and to interaction of the enzyme with coenzyme derivatives and inhibitors. Peak A moves from 15.4 to 17.4 ppm as the pH is lowered, while peak B moves in the opposite direction from 14.7 to 13.7 ppm, both with an apparent pKa of 6.15. This pKa is associated with deprotonation of the imine nitrogen at the Schiff base linkage of the coenzyme with K258 of the enzyme. In spectra of enzyme containing pyridoxamine 5'-phosphate, peak A is observed at 16.5 ppm and peak B is at 13.9 ppm over a broad pH range. Peaks A and B are found at 17.8 and 14.0 ppm, respectively, for the enzyme complex with glutarate. When alpha-methylaspartate is added to the enzyme several new resonances appear in the spectrum, which are attributed to formation of the external aldimine. The position of peak A in spectra of various forms of the enzyme is interpreted to reflect the electronic distribution in the coenzyme ring. Several other peaks in this region of the spectrum also are sensitive to changes in pH or the addition of inhibitors. Some possible assignments of these resonances are discussed.
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PMID:NMR observation of exchangeable protons of pyridoxal phosphate and histidine residues in cytosolic aspartate aminotransferase. 165 26

Stereochemical studies of three pyridoxal phosphate dependent decarboxylases and serine hydroxymethyltransferase have allowed the dispositions of conjugate acids that operate at the C alpha and C-4' positions of intermediate quinoids to be determined. Kinetic work with the decarboxylase group has determined that two different acids are involved, a monoprotic acid and a polyprotic acid. The use of solvent kinetic isotope effects allowed the resolution of chemical steps in the reaction coordinate profile for decarboxylation and abortive transamination and pH-sensitivities gave the molecular pKa of the monoprotic base. Thus the epsilon-ammonium group of the internal aldimine-forming lysine residue operates at C-4'-si-face of the coenzyme and the imidazolium side chain of an active site histidine residue protonates at C alpha from the 4'-si-face. Histidine serves two other functions, as a base in generating nitrogen nucleophiles during both transaldimination processes and as a binding group for the alpha-carboxyl group of substrates. The latter role for histidine was determined by comparison of the sequences for decarboxylase active site tetrapeptides (e.g. -S-X-H-K-) with that for aspartate aminotransferase (e.g. -S-X-A-K-) where it was known, from X-ray studies, that the serine and lysine residues interact with the coenzyme. By using the Dunathan Postulate, the conformation of the external aldimine was modified, and without changing the tetrapeptide conformation, the alanine residue was altered to a histidine. This model for the active site of a pyridoxal dependent decarboxylase was consistent with all available stereochemical and mechanistic data.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A structural and mechanistic comparison of pyridoxal 5'-phosphate dependent decarboxylase and transaminase enzymes. 167 32

Methanosarcina barkeri was able to grow on L-alanine and L-glutamate as sole nitrogen sources. Cell yields were 0.5 g/l and 0.7 g/l (wet wt), respectively. The mechanism of ammonia assimilation in Methanosarcina barkeri strain MS was studied by analysis of enzyme activities. Activity levels of nitrogen-assimilating enzymes in extracts of cells grown on different nitrogen sources (ammonia, 0.05-100 mM; L-alanine, 10 mM; L-glutamate, 10 mM) were compared. Activities of glutamate dehydrogenase, glutamate synthase, glutamine synthetase, glutamate oxaloacetate transaminase and glutamate pyruvate transaminase could be measured in cells grown on these three nitrogen sources. Alanine dehydrogenase was not detected under the growth conditions used. None of the measured enzyme activities varied significantly in response to the NH4+ concentration. The length of the poly-gamma-glutamyl side chain of F420 derivatives turned out to be independent of the concentration of ammonia in the culture medium.
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PMID:Ammonia assimilation and glutamate incorporation in coenzyme F420 derivatives of Methanosarcina barkeri. 167 22

An increased aspartate transaminase in the liver of dietary (post-cafeteria) obese rats was found. It was consistent with the functionality of the malate-aspartate shuttle, that could be responsible for enhancement of metabolic efficiency. The muscle and intestine of obese rats showed a greater capacity for alanine and glutamine synthesis than the controls. Furthermore, enterocyte adaptations in the obese rats indicated higher capabilities for the intake of nitrogen than in the controls. In conclusion, the pattern of amino-acid enzyme activities reflected adaptations to keep from amino nitrogen depletion in dietary obesity which were compatible with an enhancement of the metabolic efficiency.
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PMID:Dietary obesity shows adaptations of amino-acid metabolism on enzyme activities to save amino nitrogen. 168 27

The time course of changes in serum proteins and other blood constituents after eccentric exercise of the forearm flexors by six nonweight-trained female subjects (age, 19.7 +/- 1.9 years) was investigated. Eccentric muscle actions are those in which the muscle lengthens as it exerts force, as when a person lowers a weight. Serum levels of creatine kinase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma-glutamyl transpeptidase, myoglobin, as well as urea nitrogen, uric acid, creatinine, calcium, and phosphorus were examined before and for 6 days after exercise. Creatine kinase increased dramatically (peak value ranged from 6740 to 24,200 U/L) and aspartate aminotransferase, lactate dehydrogenase, alanine aminotransferase, and myoglobin followed the same time course as creatine kinase, but their peak values were lower. These proteins did not increase significantly until 48 hours after exercise and reached peak values 3 to 5 days after exercise. Alkaline phosphatase, gamma-glutamyl transpeptidase, uric acid, urea nitrogen, creatinine, calcium, and phosphorus showed no change. There is either a delay in muscle protein release by damaged muscle fibers, or the proteins are unable to leave the interstitial area for the 24 to 48 hour period after exercise. Because of the long delay, care should be taken when blood protein levels are interpreted in persons who have exercised strenuously (even if only for a short period of intense effort) several days before any diagnostic tests are performed.
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PMID:Time course of serum protein changes after strenuous exercise of the forearm flexors. 174 Jun 32

In 1983 and 1984 blood was collected from 79 cottontail rabbits (Sylvilagus floridanus) confined to an outdoor enclosure in southern Illinois to establish reference values for hematology and serum chemistry. Packed cell volume, sodium, potassium, chloride, glucose, calcium, carbon dioxide, blood urea nitrogen, creatinine, uric acid, cholesterol, albumin, bilirubin, alkaline phosphatase, aspartate transaminase, alanine aminotransaminase, total protein, albumin/globulin ratio, and osmolality were measured. Sex and age (adult versus juvenile) of rabbit as well as season (June to September versus October to May) and method of capture (trap versus shot) variously affected most hematology and serum chemistry variables.
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PMID:Hematology and serum chemistry of cottontail rabbits of southern Illinois. 175 30

Effects of administration of triflupromazine were evaluated in 11 adult domesticated camels (Camelus dromedarius) weighing 403 +/- 29.5 kg (Mean +/- SE). Six camels were used to evaluate sedative properties of the drug and its effects on haematological and blood biochemical parameters. In the remaining 5 camels, effects on haemodynamics, acid base status and blood gases were studied. In all the animals triflupromazine was administered intramuscularly in the gluteal region at the rate of 2 mg/kg. Camels voluntarily sat down 48.9 +/- 5.4 min after administration of the drug but stood up again if disturbed. Drowsiness, drooping of lower lip and salivation were evident. The animals stood on their own and started walking with ataxia after 159 +/- 7 min and recovered completely from the effect of drug within 259 +/- 23 min. The drug caused a significant tachycardia and a moderate hypotension. The decrease in central venous pressure was also significant. Rectal temperature, respiratory rate, acid base status, blood gases, haemoglobin concentration, packed cell volume, total erythrocyte count, total leucocyte count, differential leukocyte count, blood urea nitrogen, plasma alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, alkaline phosphatase, blood glucose and plasma concentrations of sodium, potassium, chloride and inorganic phosphate were not significantly affected by triflupromazine.
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PMID:Evaluation of triflupromazine as a sedative in camels (Camelus dromedarius). 177 79

Hydrated sodium calcium aluminosilicate (HSCAS), an anticaking agent for mixed feed, was added to the diets of growing wethers (mean body weight, 34.0 kg) and was evaluated for its ability to diminish the clinical signs of aflatoxicosis. The experimental design consisted of 4 treatment groups of 5 wethers each, consuming concentrations of 0 g of HSCAS and 0 g of aflatoxin (AF)/kg of feed (control; group 1); 20 g of HSCAS/kg (2.0%; group 2), 2.6 mg of AF/kg (group 3); or 20 g of HSCAS (2.0%) plus 2.6 mg of AF/kg (group 4). Wethers were maintained in indoor pens, with feed and water available ad libitum for 42 days. Lambs were observed twice daily and weighed weekly, and blood samples were obtained every 2 weeks for hematologic and serum biochemical analyses and for measurement of mitogen-induced lymphocyte-stimulation index. At the termination of the study, wethers were euthanatized and necropsied. Body weight gain was diminished significantly (P less than 0.05) by consumption of 2.6 mg of AF/kg of feed, whereas body weight of lambs consuming HSCAS plus AF did not differ from that of control wethers. The AF-alone treatment increased serum aspartate transaminase and gamma-glutamyltransferase activities, prothrombin time, and cholesterol, uric acid, and triglyceride values and decreased albumin, glucose, and urea nitrogen values, and urea-to-creatine ratio.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Diminution of aflatoxin toxicity to growing lambs by dietary supplementation with hydrated sodium calcium aluminosilicate. 185 May 85

These studies were designed to determine if macular mutant mouse, which is a proposed animal model of Menkes' kinky-hair disease, is sensitive to the acute toxic effect of Cu as compared to normal and heterozygote mice. Single sc injection of Cu were administered to 6- to 8-day-old mice, and mortalities were recorded for 30 days. The copper treatment at high doses (12 to 25 mg Cu/kg) was very toxic to mutant mice as compared to normal mice, and almost all mutant mice died within 10 days after injection. The effect of Cu toxicity on heterozygote mice was intermediate. The LD50 values 3 days after injection of Cu were 29.5 mg Cu/kg for normal mice, 23.5 mg Cu/kg for heterozygote mice, and 15.5 mg Cu/kg for mutant mice. In Cu-injected mutant mice (11 and 18 mg Cu/kg), significant elevations in serum aspartate aminotransferase and lactate dehydrogenase activity occurred as compared to Cu-injected normal and heterozygote mice. However, no significant elevations in serum creatinine and urea nitrogen contents in Cu-injected mutant were observed as compared to normal and heterozygote mouse. No significant differences in hepatic metallothionein(MT) and MT-1 mRNA, and serum ceruloplasmin oxidase activity levels were observed between Cu-injected normal and mutant mouse. These results indicated that macular mutant mice was sensitive to the acute toxic or hepatotoxic effects of Cu as compared to normal and heterozygote mice.
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PMID:Copper-induced toxicity in macular mutant mouse: an animal model for Menkes' kinky-hair disease. 187 75


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