The complete amino acid sequences of cytosolic and mitochondrial aspartate aminotransferases from horse heart,and inferences on evolution of the isoenzymes |
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Authors: | Shawn Doonan Filippo Martini Sebastiana Angelaccio Stefano Pascarella Donatella Barra Francesco Bossa |
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Institution: | (1) Department of Biochemistry, University College, Cork, Ireland;(2) Dipartimento di Scienze Biochimiche e Centro di Biologia Molecolare del CNR, Università di Roma, Città Universitaria, 00185 Rome, Italy |
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Abstract: | Summary We report here the complete amino acid sequences of the cytosolic and mitochondrial aspartate aminotransferases from horse heart. The two sequences can be aligned so that 48.1% of the amino acid residues are identical. The sequences have been compared with those of the cytosolic isoenzymes from pig and chicken, the mitochondrial isoenzymes from pig, chicken, rat, and human, and the enzyme fromEscherichia coli. The results suggest that the mammalian cytosolic and mitochondrial isoenzymes have evolved at equal and constant rates whereas the isoenzymes from chicken may have evolved somewhat more slowly. Based on the rate of evolution of the mammalian isoenzymes, the geneduplication event that gave rise to cytosolic and mitochondrial aspartate aminotransferases is estimated to have occurred at least 109 years ago. The cytosolic and mitochondrial isoenzymes are equally related to the enzyme fromE. coli; the prokaryotic and eukaryotic enzymes diverged from one another at least 1.3×109 years ago. |
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Keywords: | Aspartate aminotransferase Isoenzyme Protein evolution Mitochondria |
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