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)

Cytoplasmic (c) and mitochondrial (m) isoenzymes of aspartate aminotransferase (AAT, EC 2.6.1.1.) were isolated from rat heart extracts by electrophoresis in agar gel. Their pH optima and Km values were estimated; optimal conditions for estimation of the enzymatic activities are reported. Isadrine activated and adrenaline inhibited the cAAT activity. Noradrenaline did not affect the activity of both isoenzymes. Phentolamine, as contrary to obsidane which decreased the activity of both isoenzyme, activated the isoenzymes; the effect was partially decreased by obsidane. Phentolamine did not alter the noradrenaline effect on either mAAT or cAAT; it decreased significantly the free form of the mAAT activity only. Results of the experiments with administration of adrenomimetic drugs suggested that adrenaline and noradrenaline-isadrine had different sites of attachment through which they mediated their action on aspartate aminotransferase in rat heart mitochondria.
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PMID:[Role of adrenoreceptors in regulating aspartate aminotransferase isoenzyme activity in albino rat hearts]. 2 53

Antisera against rat liver aspartate aminotransferase (EC 2.6.1.1) isozymes were used to study the activity and immunologic pattern of these isozymes in the livers of the rat, mouse, hamster, gerbil and in Ehrlich ascites cells. A double immunodiffusion precipitin test and immunoelectrophoresis showed that, except for the gerbil, there was a pattern of identity of AAT isozymes in the presence of either the antianionic or the anticationic antisera. Although gerbil AAT isozymes are immunochemically different from those of the other rodents studied, they were inactivated by the respective antiserum in a manner similar to that observed with the other species. This may suggest that antigenic determinants at the catalytic site of each of the liver aspartate aminotransferase isozymes are least likely to change throughout the evolutionary process.
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PMID:Immunochemical pattern of aspartate aminotransferase isozumes in servral rodents and in Ehrlich ascites cells (38549). 4 35

The effect of potassium depolarization and N-methyl-D-aspartate (NMDA) on the activity of aspartate aminotransferase (AAT; EC 2.6.1.1), an enzyme suggested to be involved in neurotransmitter glutamate synthesis, was studied in cultured cerebellar granule neurons. Both KCl and NMDA increased AAT activity in a dose-dependent manner. When cells were treated 48-72 hr with 40 mM KCl or 150 microM NMDA the AAT was enhanced about 65-75%. The EC50 for NMDA and KCl were 25 microM and 17 mM, respectively. The effect of NMDA and KCl was specific for AAT without affecting the activity of other enzymes like lactate dehydrogenase or protein content and it was observed only in granule cells but not in astrocytes or cortical neurons. The effect of KCl was not mediated by an activation of excitatory amino acid receptors and was Ca(++)-dependent. The effect of NMDA was completely blocked by Mg++ and NMDA antagonists. The increase of AAT induced by AAT and KCl was blocked by cycloheximide and actinomycin D, suggesting an involvement of de novo synthesis of proteins and RNA. Kainic acid and quinolinic acid were also effective in increasing the AAT activity. The action of kainate was less effective than that of NMDA and it was observed only at relatively low concentrations (10 microM). Quinolinic acid raised the activity of AAT about 45% at a concentration of 500 microM. Other non-NMDA agonists did not modify the AAT activity. From these findings we can conclude that NMDA and KCl exert a trophic action on cerebellar granular neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of potassium and N-methyl-D-aspartate on the aspartate aminotransferase activity in cultured cerebellar granule cells. 145 88

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

We have isolated an alfalfa leaf cDNA clone that encodes aspartate aminotransferase (AAT, EC 2.6.1.1) by direct complementation of an Escherichia coli aspartate auxotroph with a plasmid cDNA library. DNA sequence analysis of the recombinant plasmid, pMU1, revealed that a 1514 bp cDNA was inserted in the correct orientation and in-frame with the start of the lacZ coding sequence in the vector, pUC18. The resulting fusion protein is predicted to be 424 amino acids in length with a molecular weight of 46387 Daltons. The cDNA-encoded protein has a characteristic pyridoxal phosphate attachment site motif and has substantial amino acid sequence homology to both animal and bacterial AATs. Plasmid pMU1 encodes an AAT with a Km for aspartate of 3.3 mM, a Km for 2-oxoglutarate of 0.28 mM, and a pH optimum between 8.0 and 8.5. Several lines of evidence including Western blot analysis, the isoelectric point of the encoded protein, and the effect of pH on the activity of the fusion protein, suggest that the cDNA encodes the isozyme AAT-1 rather than AAT-2. Northern blot analysis showed that the aat-1 clone hybridized to a 1.6 kb transcript present in alfalfa leaves, roots and nodules. The relative concentrations of aat-1 mRNA in these tissues were 1:2:5, respectively. Thus, transcription of aat-1 appears to be induced during nodule development. Southern blot analysis suggested that AAT-1 in alfalfa is encoded by either a single-copy gene or a small, multigene family.
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PMID:Isolation and analysis of a cDNA clone that encodes an alfalfa (Medicago sativa) aspartate aminotransferase. 175 49

The mitochondrial (m-AAT) and the cytoplasmic (c-AAT) isoenzyme activities of the glutamate synthesizing enzyme aspartate aminotransferase have been localized in the rat retina on the ultrastructural level using enzyme histochemistry. Reaction product of c-AAT was found selectively in cone pedicles, in presynaptic terminals of a subpopulation of amacrine cells and of horizontal cell processes, which are connected to rods. Rod spherules, terminals of cone-related horizontal cells and of bipolar cells reacted negatively, as well as ganglion cells, nerve fibre layer and optic nerve, m-AAT reaction product was found in all neuronal structures, most densely in the photoreceptor inner segments. The localization of c-AAT activity is in accordance with its presumed meaning in the production of releasable glutamate.
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PMID:Cytochemical demonstration of aspartate aminotransferase activity in the rat retina. 205 2

An investigation of the crystal structure of cytosolic pig-heart aspartate aminotransferase (AAT, E.C.2.6.1.1) was carried out to determine the structural requirements for ligand recognition by the active site. Structural differences were observed between the two active sites of the AAT dimer. The natural ligand, L-aspartate, was docked into both active sites using various methods. However, due to structural differences, the ligand was able to form all the necessary interactions for initial binding in only one of the active sites. The program GRID (P.J. Goodford, J. Med. Chem. 1985, 28, 849-857) was used to predict favorable binding sites for the functional groups of the aspartate ligand. These binding sites corresponded to the position of the docked aspartate ligand, indicating that substrate recognition takes place before any major conformational changes occur within the enzyme.
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PMID:Aspartate aminotransferase: investigation of the active sites. 228 53

1. Gel electrophoresis of aspartate aminotransferase released from boar spermatozoa after cold shock showed one band migrating towards anode. 2. Physico-chemical and kinetic properties of isolated enzyme were similar to cytoplasmic isoenzyme of AAT from somatic tissues.
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PMID:Isolation and characteristics of aspartate aminotransferase from boar spermatozoa. 251 80

The subcellular location of aspartate aminotransferase isozymes (EC 2.6.1.1) in the genus Capsella (Brassicaceae) was studied. The diploid species C. grandiflora and C. rubella have three AAT isozymes, including one located in the plastids. Each locus is duplicated in the tetraploid Capsella bursa-pastoris. Variation at the plastid-coding locus exceeded that at the other loci. C. bursa-pastoris had some unique alleles not detected in the diploid species. Segregation in open-pollinated families revealed that Capsella grandiflora was outcrossing, whereas C. rubella was highly inbred, with most populations homozygous or uniform at all three loci. Inheritance in the tetraploid colonizer C. bursa-pastoris is disomic. This species was also predominantly selfing with outcrossing rates between 2% and 10%.
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PMID:Aspartate aminotransferase isozymes in the genus Capsella (Brassicaceae): subcellular location, gene duplication, and polymorphism. 271 24

Cytosolic and mitochondrial isoenzymes of aspartate aminotransferase (EC 2.6.1.1) were purified to homogeneity from chicken liver, without previous fractionation of the subcellular components. The procedure includes initial heat treatment and ammonium sulfate fractionation. The two isoenzymes can then be separated by a DEAE-Sepharose chromatography using a linear gradient of L-aspartate (reaction substrate). The separated fractions can be further purified by a parallel step with HA-Ultrogel prior to octyl-Sepharose (c-AAT) and CM-Sepharose (m-AAT) chromatographies. Michaelis constants, pI values, inhibition by adipate and subforms generation with time were studied for both isoenzymes.
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PMID:Simultaneous purification and characterization of aspartate aminotransferase isoenzymes from chicken liver. 323 18


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