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)

The production, purification and analysis of peptide derived by digestion of mitochondrial aspartate aminotransferase with thermolysin and chymotrypsin are described. Despite the complexity of the peptide mixture obtained and the relative shortness of the fragments produced, these digests proved to be very useful for the completion of the primary structure determination of the enzyme. In fact, information for 87% of the total structure was contributed by thermolytic peptides, and for 89% by the chymotryptic ones. Moreover some of these peptides were essential for elucidating controversial points of the sequence.
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PMID:The primary structure of mitochondrial aspartate aminotransferase from pig heart: peptides obtained by cleavage with thermolysin and chymotrypsin. 55 5

The analysis of conformational transitions using limited proteolysis was carried out on a hyperthermophilic aspartate aminotransferase isolated from the archaebacterium Sulfolobus solfataricus, in comparison with pig cytosolic aspartate aminotransferase, a thoroughly studied mesophilic aminotransferase which shares about 15% similarity with the archaebacterial protein. Aspartate aminotransferase from S. solfataricus is cleaved at residue 28 by thermolysin and residues 32 and 33 by trypsin; analogously, pig heart cytosolic aspartate aminotransferase is cleaved at residues 19 and 25 [Iriarte, A., Hubert, E., Kraft, K. & Martinez-Carrion, M. (1984) J. Biol. Chem. 259, 723-728] by trypsin. In the case of aspartate aminotransferase from S. solfataricus, proteolytic cleavages also result in transaminase inactivation thus indicating that both enzymes, although evolutionarily distinct, possess a region involved in catalysis and well exposed to proteases which is similarly positioned in their primary structure. It has been reported that the binding of substrates induces a conformational transition in aspartate aminotransferases and protects the enzymes against proteolysis [Gehring, H. (1985) in Transaminases (Christen, P. & Metzler, D. E., eds) pp. 323-326, John Wiley & Sons, New York]. Aspartate aminotransferase from S. solfataricus is protected against proteolysis by substrates, but only at high temperatures (greater than 60 degrees C). To explain this behaviour, the kinetics of inactivation caused by thermolysin were measured in the temperature range 25-75 degrees C. The Arrhenius plot of the proteolytic kinetic constants measured in the absence of substrates is not rectilinear, while the same plot of the constants measured in the presence of substrates is a straight line. Limited proteolysis experiments suggest that aspartate aminotransferase from S. solfataricus undergoes a conformational transition induced by the binding of substrates. Another conformational transition which depends on temperature and occurs in the absence of substrates could explain the non-linear Arrhenius plot of the proteolytic kinetic constants. The latter conformational transition might also be related to the functioning of the archaebacterial aminotransferase since the Arrhenius plot of kcat is non-linear as well.
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PMID:Limited proteolysis as a probe of conformational changes in aspartate aminotransferase from Sulfolobus solfataricus. 155 94

The effect of various proteases (trypsin, chymotrypsin, subtilisin, protease 401, and thermolysin) on the mitochondrial isoenzyme (m-AST) and cytoplasmic isoenzyme (c-AST) of human and swine aspartate aminotransferase (AST;EC 2.6.1.1) was evaluated. All procedures including the reaction with proteases and the subsequent determination of the AST activity were carried out in an automatic analyzer. The mammalian c-AST was efficiently inactivated by chymotrypsin, subtilisin and protease 401 while m-AST activity decreased very slowly with these proteases. Thermolysin and trypsin showed much less effect on c-AST activity. Especially, chymotrypsin at concentrations of 0.5-1.0 g/L inactivated human c-AST almost completely but showed no detectable inactivating effect on m-AST. Thus chymotrypsin appears to be the most suitable protease for the differential determination of AST isoenzymes in human serum. Further studies on the effects of proteases with AST from other species showed that Escherichia coli AST resembled mammalian m-AST while Pseudomonas AST resembled c-AST.
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PMID:Determination of human aspartate aminotransferase isoenzymes by their differential sensitivity to proteases. 306 46

The amino acid sequences of 39 tryptic peptides from carboxymethylated mitochondrial aspartate aminotransferase from pig heart muscle were analyzed. The peptides were purified by gel filtration, ion exchange column chromatography, paper chromatography, and high voltage paper electrophoresis, and their sequences were examined by manual Edman degradation, carboxypeptidase digestion, and fragmentation with thermolysin or chymotrypsin. These peptides accounted for 318 of the total 401 amino acid residues in the protein subunit.
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PMID:Complete amino acid sequence of mitochondrial aspartate aminotransferase from pig heart muscle. Tryptic peptides. 739 Oct 10