Purification and Properties of an Aminopeptidase from Escherichia coli

An aminopeptidase from Escherichia coli has been purified to homogeneity and crystallized. This peptidase is responsible for about 65% of the hydrolytic activity found in crude extracts toward the substrate methionylalanylserine. It resembles the so-called leucine aminopeptidase of hog kidney in several respects, including size, metal requirements, and peptide specificity. Evidence based on substrate specificity suggests that this E. coli peptidase is not involved in cleavage of N-terminal methionine from nascent protein chains.