Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.6.1.1 (aspartate aminotransferase)
 21,665 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Frontal and zonal analysis of the chromatography of aspartate aminotransferase (EC2.61.1), pig heart cytosolic enzyme, on Bio-Gel P150 shows that holo- and apoenzyme can dissociate at pH 8.3. Ultracentrifugation and fluorescence depolarization confirm this result. Kinetic analysis of the fluorescence depolarization experiments favors a biphasic phenomenon: a few minutes for the faster one and several hours for the slower one. The apparent dissociation constant is 0.8 muM for the apoenzyme and 0.18 muM for the pyridoxal 5'-phosphate form of the holoenzyme. In the presence of sucrose or 0.1 M L-aspartate or a mixture of 70 mM L-glutamate and 2 mM alpha-ketoglutarate, the holoenzyme is dimeric at concentrations higher than 5 nM. The addition of a mixture of the substrates L-glutamate and alpha-ketoglutarate to a monomeric holoenzyme leads to dimerization. The stability of the dimeric form is in the order: holoenzyme + substrates greater than apoenzyme.
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PMID:Dissociation of aspartate aminotransferase into subunits. Effect of ligands upon this dissociation. 119 65

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

A peptide (extra signal peptide) comprising amino acids 1-29 of pig liver pre-mitochondrial aspartate aminotransferase (p-mAAT) was synthesized chemically. The peptide was found to block the import of rat liver p-mAAT into rat liver mitochondria. An antibody raised against the peptide immunoprecipitated rat liver p-mAAT synthesized in a rabbit reticulocyte cell-free translation system. These results suggested that the extra signal peptide sequence of p-mAAT is essential for import of p-mAAT into the mitochondria and that there is structural homology between the extra signal peptides of pig and rat liver p-mAAT. An anti-idiotypic antibody against the peptide was also prepared and purified by affinity chromatography on an Affi-Gel 10 anti-peptide IgG column and was then characterized.
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PMID:An antibody and anti-idiotypic antibody against the extra signal peptide of pre-aspartate aminotransferase. 282 94

The mitochondrial enzymes citrate synthase, malate dehydrogenase, and aspartate aminotransferase were purified to homogeneity from porcine hearts by use of Bio-Rex 70, carboxymethylcellulose CM32, and Affi-Gel blue chromatography. This procedure provides relatively rapid, large-scale preparation of the three enzymes based on their differential binding to commercially available cation-exchange resins followed by a final affinity chromatography step.
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PMID:Concomitant purification of three porcine heart mitochondrial enzymes: citrate synthase, aspartate aminotransferase, and malate dehydrogenase. 398 11

Pretreatment with Mn2+ is known to produce tolerance to Cd2+-induced lethality. This study was designed to determine the mechanism of tolerance to Cd2+-induced lethality and hepatotoxicity following Mn2+ pretreatment. Rats given 36 mumoles Cd2+/kg, i.v., died within 10-20 hr while only one of nine rats pretreated with Mn2+ (250 mumoles/kg, s.c., 48 and 24 hr prior to Cd2+ challenge) died. Ten hours after Cd2+, plasma aspartate aminotransferase and sorbitol dehydrogenase activities were elevated markedly, and extensive histopathologic lesions of the liver were evident in control rats but not in Mn2+-pretreated rats. To examine the mechanism of this tolerance, distribution of Cd2+ to fourteen organs and the subcellular distribution in six organs were determined in control and Mn2+-pretreated rats. Two hours after challenge (31 mumoles Cd2+/kg, i.v., 0.75 microCi 109Cd2+/mumol Cd2+), the distribution of Cd2+ to liver markedly increased after Mn2+ pretreatment with concomitant decreases in other tissues. Mn2+ pretreatment also resulted in a marked difference in the hepatic subcellular distribution of Cd2+ with more present in cytosol and less associated with organelles. Gel-filtration chromatography indicated that most cytosolic Cd2+ was bound to a low molecular weight protein. Isolation and partial characterization of this protein suggest that it is identical to metallothionein (MT); it had a similar relative elution following gel-filtration chromatography, had low absorbance at 280 nm and, after separation into two isoproteins by DEAE A-25 anion exchange chromatography, had the same mobility after electrophoresis on non-denaturing polyacrylamide gels as Cd2+-induced metallothioneins. These data suggest that Mn2+ pretreatment reduces Cd2+-induced hepatotoxicity by altering the hepatic subcellular distribution of Cd2+ with more Cd2+ binding to MT in the cytosol. This decreased hepatotoxicity is probably responsible for tolerance to Cd2+-induced lethality.
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PMID:Mechanism of manganese-induced tolerance to cadmium lethality and hepatotoxicity. 399 53

Pretreatment with Zn is known to produce tolerance to several toxic effects of Cd. This study was designed to determine if zinc pretreatment decreased Cd-induced lethality and hepatotoxicity. Rats given 4.0 mg Cd/kg, iv, died within 10 to 20 hr while there was no mortality in rats pretreated with Zn (12 mg Zn/kg, sc, 48 and 24 hr prior to Cd challenge). Ten hr after Cd, plasma aspartate aminotransferase and sorbitol dehydrogenase activities were markedly elevated and extensive histopathologic lesions of the liver were evident in control rats while such injury was not evident in Zn-pretreated rats. To examine the mechanism of this tolerance, distribution of Cd to 14 organs and the subcellular distribution in 6 organs (liver, kidneys, intestines, heart, spleen, and testes) was determined in control and Zn-pretreated rats. Two hours after challenge (3.5 mg Cd/kg, iv, 7 microCi 109Cd/mg Cd), the distribution of Cd to the liver markedly increased after Zn pretreatment without concomitant decreases in other tissues. Zn pretreatment resulted in distribution of more Cd to hepatic cytosol and less associated with endoplasmic reticulum. Gel filtration chromatography indicated that most cytosolic Cd was bound to metallothionein. These data suggest that Zn pretreatment reduces Cd-induced hepatotoxicity which prevents the lethal effects of Cd possibly by altering the hepatic subcellular distribution of Cd.
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PMID:Zinc-induced tolerance to cadmium hepatotoxicity. 674 Jun 79

Glutamic oxaloacetic transaminase (EC 2.6.1.1), has been prepared from the liver of Hausa he-goat (Capra hircus). 2. Gel filtration of the liver extract presents evidence of two molecular species of the enzyme; one species (Fraction A) has a specific activity of 280 U/mg protein and the other (Fraction B) has a specific activity of 338 U/mg protein. 3. Fraction A has optimum activity at pH 6.8 and Fraction B is optimally active at pH 5.5. The observed variation in activity with pH variation may be due to ionisation of some group(s) on the enzyme. 4. Characteristic spectral changes typical of INH/GOT interactions at low and high pH values are presented. 5. Typical Dixon's plot indicates a competitive inhibition of the enzyme by INH. Ki and Km of 0.04 and 2.5 mM for Fraction A and Ki and Km of 0.098 and 4.7 mH for Fraction B have been calculated from the data. 6. These results have been discussed in the light of the properties of the enzyme from other sources.
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PMID:Isoniazid inhibition of liver glutamic oxaloacetic transaminase from the goat Capra hircus. 682 99

Twelve cyanogen bromide peptides were isolated from S-carboxymethylated mitochondrial aspartate aminotransferase and their amino acid sequences were determined. These peptides were purified first by gel filtration on a Sephadex G-75 column, and then by gel filtration on Bio-Gel, or by ion exchange chromatography on a phosphocellulose column in the presence of 8 M urea, or by both methods. Small peptides were purified by paper chromatography. The cyanogen bromide peptides accounted for 367 of the 401 amino acid residues in the subunit of the enzyme. No peptide accounting for the other 34 residues was obtained in a homogeneous state, but peptide mixtures containing this particular peptide were analyzed by various procedures including Edman degradation and digestion with Staphylococcus aureus protease. The results accounted for all 401 amino acid residues.
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PMID:Complete amino acid sequence of mitochondrial aspartate aminotransferase from pig heart muscle. Cyanogen bromide peptides. 739 Oct 11

We have expressed the DNA of the fusion of CS1 to MDH1 in Escherichia coli gltA-. The fusion protein (CS1/MDH1) is the C-terminus of CS1 linked in-frame to the N-terminus of MDH1 with a short linker of glycyl-seryl-glycyl. The fusion protein produced was isolated and purified. Gel filtration studies indicated that CS1/MDH1 had a M(r) of approximately 170,000. Western blotting analysis with SDS gel indicated a M(r) of approximately 90,000-95,000 (theoretical M(r) = 87,000). This is the expected M(r) for the fusion protein subunit. The kinetics of CS1 and MDH1 activities of the fusion protein were compared to those of the free enzymes. In addition, the effect of AAT reaction, as a competitor for the intermediate OAA of the coupled MDH-CS reaction, was examined. It was observed that AAT was a less effective competitor for OAA when the CS1/MDH1 fusion protein is used than when the separate enzymes are employed. In addition, the transient time for the coupled reaction sequence was less for the fusion protein than for the free enzymes.
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PMID:Preparation and kinetic characterization of a fusion protein of yeast mitochondrial citrate synthase and malate dehydrogenase. 791 85

Although liver fatty acid-binding protein (L-FABP) is an important binding site for various hydrophobic ligands in hepatocytes, its in vivo significance is not understood. We have therefore created L-FABP null mice and report here their initial analysis, focusing on the impact of this mutation on hepatic fatty acid binding capacity, lipid composition, and expression of other lipid-binding proteins. Gel-filtered cytosol from L-FABP null liver lacked the main fatty acid binding peak in the fraction that normally comprises both L-FABP and sterol carrier protein-2 (SCP-2). The binding capacity for cis-parinaric acid was decreased >80% in this region. Molar ratios of cholesterol/cholesterol ester, cholesteryl ester/triglyceride, and cholesterol/phospholipid were 2- to 3-fold greater, reflecting up to 3-fold absolute increases in specific lipid classes in the order cholesterol > cholesterol esters > phospholipids. In contrast, the liver pool sizes of nonesterified fatty acids and triglycerides were not altered. However, hepatic deposition of a bolus of intravenously injected [14C]oleate was markedly reduced, showing altered lipid pool turnover. An increase of approximately 75% of soluble SCP-2 but little or no change of other soluble (glutathione S-transferase, albumin) and membrane (fatty acid transport protein, CD36, aspartate aminotransferase, caveolin) fatty acid transporters was measured. These results (i) provide for the first time a quantitative assessment of the contribution of L-FABP to cytosolic fatty acid binding capacity, (ii) establish L-FABP as an important determinant of hepatic lipid composition and turnover, and (iii) suggest that SCP-2 contributes to the accumulation of cholesterol in L-FABP null liver.
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PMID:Decreased liver fatty acid binding capacity and altered liver lipid distribution in mice lacking the liver fatty acid-binding protein gene. 1267 Sep 56


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