Aminopeptidase I activities in several microorganisms.

Aminopeptidase I activity which was found to be localized in the same subcellular fraction and to be similarly heat stable was partially purified by a common procedure from Escherichia coli B, Escherichia coli K12, Enterobacter aerogenes, Salmonella typhimurium, Serratia marcescens Pseudomonas aeruginosa, and Proteus vulgaris. The enzyme preparations were shown to contain a single animopeptidase active toward both leucylleucine and methionylalanylserine by mixed-substrate initial-velocity kinetic analysis. The Km value for leucylleucine was virtually identical for the aminopeptidases of all of the organisms, as was the Km value for methionylalanylserine.