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)

A new purification method has been developed which only exploits the chromatographic behaviour of avian liver mitochondrial aspartate aminotransferase enzymes (m-AAT), and permits a rapid isolation of the protein (4 days) in large quantities with high yield and low cost. m-AAT from turkey, chicken and quail livers have been isolated by chromatography on CM-Sepharose, Sephadex G-100 and 5' AMP-Sepharose using TEA-acetate buffer (pH 7.4), and specific activities (A.E.) of 311.6, 318.9, 320.1 I.U./mg respectively were obtained. Preparations were homogeneous as judged by various electrophoretic techniques and by size exclusion HPLC. The amino acid composition, Stokes Radius, subunit molecular weight and pI values have been determined and compared, finding no appreciable differences among them. In contrast, the absorption spectrum of the turkey enzyme differed from those of chicken and quail at both pH 7.4 and pH 5.0.
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PMID:Purification and comparative studies of several mitochondrial aspartate aminotransferases from avian liver. 343 3

The aim of this study was tracing of changes in the activity of glutathione peroxidase (GSHPx), glutathione transferase (GSH S-Tr), aspartate aminotransferase (AspAT) and alanine aminotransferase (A1AT) in the brain as a result of diet enrichment with antioxidants: selenium (Se), vitamin E and vitamin B15 (pangamic acid). The experiment was carried out on Wistar rats with initial body weight 150 g. Following prolonged enrichment of diet with Se (0.1 ppm of sodium selenite), vitamin E (6 mg/100 g of diet) and vitamin B15 (2.5 mg/100 g of diet) the following results were obtained. The activity of GSHPx in brain microsomes was not changed after one year of vitamin E administration when it was measured against hydrogen hydroxide and against cumene hydrochloride; vitamin E administration increased the activity of GSH S-Tr in the cytoplasmic fraction of brain cells. Diet enrichment with selenium increased after 12 and 18 months the activity of GSHPx measured against both substrates, and GSH S-Tr activity increased considerably. Presence of vitamin B15 in diet reduced GSHPx activity after one-year or longer administration, after 18 months the activity of GSH S-Tr was reduced also. No changes were noted in the activity of AspAT and A1AT.
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PMID:The effect of long-term enrichment of diet with selenium, vitamin E and B15 on the activity of certain enzymes in rat brain. 345 69

Distributions of activity of the cytosolic (cAAT) and mitochondrial (mAAT) isoenzymes of aspartate aminotransferase and of malate dehydrogenase (MDH) were determined in guinea pig retinal layers. The distribution of total AAT activity (tAAT = cAAT + mAAT) and of mAAT activity correlated well (r = 0.88-0.91) with the distribution of MDH activity. mAAT activity was highest in the inner segments of the photoreceptors; there was a greater than twelve-fold difference between activity in that layer and in the inner retinal layers. cAAT activity was also highest in the inner segments, but the difference between the activity in the inner segments and the other layers was not nearly as great as with mAAT. cAAT activity was also relatively high in the outer nuclear layer, outer plexiform layer, and part of the inner plexiform layer. The high activity of cAAT, mAAT, and MDH in the inner segments indicates that all of these enzymes are involved in metabolic reactions related to energy production and/or to photoreceptive processes in the outer segments and, therefore, that the enzymes are probably involved in energy-related metabolism at synapses. However, other functions, including those related to neurotransmission, are not excluded.
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PMID:Distribution of activities of aspartate aminotransferase isoenzymes and malate dehydrogenase in guinea pig retinal layers. 357 59

The effects of testosterone on mitochondrial aspartate aminotransferase (mAAT) synthesis in rat ventral prostate was investigated. Procedures for the isolation, purification and characterization of AAT isozymes were developed and described. Purified mAAT preparations contained no demonstrable contaminating proteins. Prostatic mAAT was characterized as a cationic protein with an estimated mol. wt of 120,000. Cytoplasmic AAT (cAAT) isozyme was identified as an anionic protein with an estimated mol. wt of 132,000. A cytosolic cationic isozyme, similar to mAAT, was also identified as pre-mAAT. Testosterone administration to castrated rats resulted in significant increases in leucine incorporation into mAAT, in the level of mAAT, and in mAAT activity. These effects of testosterone were observed within 2 h of administration. Conversely, testosterone administration had none of these effects on cAAT or on non-AAT protein pool. Testosterone treatment did appear to increase leucine incorporation into pre-mAAT. Testosterone treatment in organ cultures and in prostate epithelial cell cultures resulted in the same stimulatory effects on mAAT as observed in the in vivo studies. The hormone was effective at the physiological concentration of 2 X 10(-9) M. These results indicated that testosterone has a rapid and specific effect on the biosynthesis of mAAT. This continues to support our proposal that testosterone regulates prostate citrate production via a stimulatory effect on mAAT which results in increased mitochondrial synthesis of citrate from aspartate.
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PMID:Testosterone stimulation of mitochondrial aspartate aminotransferase levels and biosynthesis in rat ventral prostate. 365 47

Both cytosolic (c-AAT) and mitochondrial (m-AAT) isozymes of aspartate aminotransferase (EC 2.6.1.1) appear in serum in some diseases including hepatobiliary dysfunction. The present study aimed at elucidation of the mechanism by which AAT isozymes are cleared from blood. Intravenous injection into rats of m-AAT and c-AAT purified from rat liver exhibited a biphasic clearance curve with an overall half-life of 42 min and 4.7 hr, respectively. The tissue distribution of the radioactivity following intravenous administration of 125I-labeled isozymes revealed that the liver is a major organ involved in plasma clearance of these isozymes. This conclusion was also supported by the significant retardation in plasma clearance of m-AAT in hepatectomized as well as CCl4-intoxicated rats. Furthermore, clearance rate of each AAT isozyme in an isolated perfused liver exhibited a single exponential process with the uptake rate for m-AAT being much faster than that for c-AAT. Separation of hepatocytes and sinusoidal liver cells from the rat intravenously injected with 125I-labeled AAT isozymes revealed that sinusoidal cells were responsible for the plasma clearances. In vitro uptake study showed that both isozymes were exclusively taken up by sinusoidal liver cells. The uptake rate for m-AAT was considerably greater than that for c-AAT. Endocytotic index for uptake by sinusoidal cells was 16 times with c-AAT and 34 times with m-AAT as compared with that for inulin or dextran which are taken up by fluid-phase endocytosis, suggesting involvement of adsorptive endocytosis in the uptake of the isozymes.
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PMID:Plasma clearance of intravenously injected aspartate aminotransferase isozymes: evidence for preferential uptake by sinusoidal liver cells. 399 68

Cytosolic aspartate aminotransferase (c-AAT) was purified to homogeneity from porcine heart and immunized to rabbit for production of antiserum. The purity of this enzyme protein and the specificity of its antibody were judged by silver-stained-sodium dodecyl sulfate slab gel, Western blot transfer technique, and double immunodiffusion. The antibody against porcine heart c-AAT was found to cross-react with rat c-AAT but not with nine other different enzymes from the heart, liver, and muscle. Affinity purified antibody was used to localize this isoenzyme in the rat heart, liver, kidney, and cerebellum by indirect immunoperoxidase method. It was found that, in the rat heart muscle, c-AAT reaction product was present as a linear structure parallel to the muscle fiber and along the sarcolemma. Some cardiac muscle fibers contain more reaction products than the others. In the liver, reaction product was seen unevenly distributed in the hepatocytes. The Kupffer cells and endothelia were less stained. Most of the tubular epithelia of the loop of Henle in the kidney were intensely stained. But other tubular epithelia including convoluted and collecting tubules were sporadically and less stained. The basket and stellate cells and their neuronal processes and terminals in the cerebellum were markedly stained, but the Purkinje and granule cell bodies were weakly stained. For comparison of the staining intensity with enzyme activity in each organ, the c-AAT enzyme activity was simultaneously determined in those organs. This study indicates that the presence of c-AAT is specific in different organs and tissues.
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PMID:Production and characterization of an antibody to cytosolic aspartate aminotransferase and immunolocalization of the enzyme in rat organs. 640 65

This work was undertaken as part of a search for well-characterized glycoprotein models in which both the oligosaccharide structure, the number of oligosaccharide chains, and the precise location of these chains in the protein are known. On the basis of the fact that high-affinity ligand binding sites have been defined precisely for several proteins in terms of both number and relative location, the hypothesis to be tested was that if oligosaccharide chains were covalently attached to such high-affinity ligands, they would be specifically bound in the ligand sites of the appropriate protein, thus permitting the preparation of neoglycoproteins of precise predetermined oligosaccharide valency and topography. To test this hypothesis, pyridoxal 5'-phosphate was reductively (NaB3H4) aminated with the alpha-amino group of the asparagine oligosaccharide Man6-GlcNAc2-Asn from ovalbumin. When the resulting phosphopyridoxylated oligosaccharide (PG) was added to the apo form of aspartate aminotransferase (AAT; EC 2.6.1.1, the cytosolic enzyme from pig heart, consisting of two subunits and containing two coenzyme binding sites), a 2:1 (PG-AAT) complex was formed which could be characterized on the basis of tritium content, the absorbance and fluorescence of the pyridoxamine phosphate moiety of PG, and the concanavalin A binding properties acquired by AAT through the incorporation of the oligosaccharide. As expected from the established properties of the holoenzyme, the AAT-PG complex is stable in the absence of phosphate or vitamin B6 derivatives and can be dialyzed for 24 h without any significant loss of PG. According to the three-dimensional model of AAT, the oligosaccharide chain of PG should be partially masked in the coenzyme binding pocket.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Neoglycoproteins: preparation of noncovalent glycoproteins through high-affinity protein- (glycosyl) ligand complexes. 646 43

Electrophoretic variation involving three alleles is described for the duplicated loci for supernatant aspartate aminotransferase (AAT-1,2), from muscle extracts of brook trout. Both loci exhibit largely disomic inheritance. Exceptional progeny types are proposed to be the result of a form of tetrasomic inheritance. Nonrandom segregation was found among the progeny of males doubly heterozygous for AAT markers; where so-called linkage phase was known, this nonrandom assortment was shown to be pseudolinkage (78.9 percent recombination). Analyses of joint segregation of triply heterozygous males for the AAT-(1,2) loci and for the single alpha glycerophosphate dehydrogenase locus (AGP-1) revealed true linkage of AGP-1 with one AAT locus (mean r = 11 percent), but pseudolinkage with the other AAT locus (r = 74 percent). Intraindividual variation for homoeologous multivalent pairing of two acrocentric with two metacentric chromosomes in males, but with bivalent pairing in females, is proposed to account for pseudolinkage and for the tetrasomically inherited types.
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PMID:Pseudolinkage of the duplicate loci for supernatant aspartate aminotransferase in brook trout, Salvelinus fontinalis. 677 6

The rabbit antiserum and mouse monoclonal hybridoma antibody against porcine cytosolic aspartate aminotransferase (c-AAT) (or cytosolic glutamic oxaloacetic transaminase (c-GOT)) were produced and compared for the localization of c-AAT in rat liver. An indirect immunocytochemical technique was performed using peroxidase-conjugated goat immunoglobulin (Ig) G anti-rabbit IgG and peroxidase-conjugated rabbit IgG anti-mouse IgG as the second antibody. Rats were perfused with paraformaldehyde-lysine-periodate fixative and the liver fragments were immersed in 4% paraformaldehyde and transferred to 10% dimethyl sulfoxide overnight and subjected to cryostat sectioning. The rabbit IgG antibody, 3 individual monoclonal antibodies, and a mixture of these 3 monoclonal antibodies were applied to the tissue sections, respectively, using the same concentration. Under the same experimental conditions, the c-AAT was localized in each individual hepatocyte by both monoclonal and polyclonal antibodies. However, a mixture of three monoclonal antibodies gave stronger staining than a single monoclonal antibody; although two antibodies yield more intense staining than just one, it was still less intense than for three. The conventional rabbit polyclonal antibody against c-AAT produced more reaction product than the combined three monoclonal antibodies. It is concluded that for immunocytochemical study, the use of a single monoclonal antibody is sensitive enough to localize its tissue antigen under the present experimental condition. To obtain a stronger reaction product, a combination of several monoclonal antibodies, at least three or more, may give better staining.
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PMID:A comparative study of polyclonal and monoclonal antibodies for immunocytochemical localization of cytosolic aspartate aminotransferase in rat liver. 685 5

Activities of the cytoplasmic and mitochondrial isozymes of aspartate aminotransferase (aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1, AAT) in transplantable mouse hepatomas BW7756 and H-4 are reduced when compared to normal adult liver. Both proteins have been purified to homogeneity from a single preparation of mouse liver and monospecific antibodies raised to each isozyme. By quantitative immunotitration analysis, the activity of each isozyme in liver and hepatoma has been shown to correlate with levels of immunoprecipitable protein. Furthermore, for each isozyme, the liver versus hepatoma species is indistinguishable by heat inactivation kinetics, Km's for substrates, and molecular weights. Thus, the reduction of mitochondrial and cytoplasmic AAT activities in hepatoma tissue is due not to alterations in the catalytic activity of the enzyme molecules, but to a decrease in the number of enzyme molecules present. Turnover of the isozymes was studied in liver and hepatoma tissue using in vivo radiolabeling and specific immunoprecipitation techniques. The cytoplasmic isozyme has a similar rate of degradation in liver and hepatoma, while the rate of synthesis of this isozyme in hepatoma is approximately tenfold less than in liver. The mitochondrial isozyme is also degraded at a similar rate in both tissues, but the rate of synthesis is sixfold greater in normal liver tissue than in hepatoma. It is concluded that decreased amounts of both isozymes in hepatoma as compared to liver are the result of a reduction in the rate of synthesis of each isozyme without any change in the rate of degradation.
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PMID:Turnover of cytoplasmic and mitochondrial aspartate aminotransferase isozymes in mouse liver and transplantable hepatomas. 685 79


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