The primary structure of omega-amino acid:pyruvate aminotransferase

The complete amino acid sequence of bacterial omega-amino acid:pyruvate aminotransferase (omega-APT) was determined from its primary structure. The enzyme protein was fragmented by CNBr cleavage, trypsin, and Staphylococcus aureus V8 digestions. The peptides were purified and sequenced by Edman degradation. omega-ATP is composed of four identical subunits of 449 amino acids each. The calculated molecular weight of the enzyme subunit is 48,738 and that of the enzyme tetramer is 194,952. No disulfide bonds or bound sugar molecules were found in the enzyme structure, although 6 cysteine residues were determined per enzyme subunit. Sequence homologies were found between an omega-aminotransferase, i.e. mammalian and yeast ornithine delta-aminotransferases, fungal gamma-aminobutyrate aminotransferase and 7,8-diaminoperalgonate aminotransferase, and 2,2-dialkylglycine decarboxylase. The enzyme structure is not homologous to those of aspartate aminotransferases (AspATs) including the enzymes of Escherichia coli and Sufolobus salfactaricus, though significant homology in the three-dimensional structures around the cofactor binding site has been found between omega-APT and AspATs (Watanabe, N., Sakabe, K., Sakabe, N., Higashi, T., Sasaki, K., Aibara, S., Morita, Y., Yonaha, K., Toyama, S., and Fukutani, H. (1989) J. Biochem. 105, 1-3).