The primary structure of leucine aminopeptidase from bovine eye lens

The amino acid sequence of bovine eye lens leucine aminopeptidase has been determined. Cyanogen bromide fragments, the COOH-terminal hydroxylamine fragment, and a large fragment obtained by digestion with Staphylococcus aureus protease were isolated from reduced and S-alkylated leucine aminopeptidase. The amino acid sequences of these fragments were determined by automated sequence analysis, by manual direct Edman degradation, and by the dansyl-Edman technique. Overlapping peptides were obtained by tryptic digestion of the S-alkylated protein or the citraconylated S-alkylated protein. The polypeptide chain of leucine aminopeptidase comprises 478 residues, corresponding to a molecular weight of 51,691. No significant sequence homology with any other published protein primary structure could be detected. This is the first report of a complete amino acid sequence of an enzyme belonging to the class of two metal peptidases.