Purification and characterization of a novel tripeptidyl aminopeptidase from Streptomyces lividans 66

An extracellular tripeptidyl aminopeptidase has been purified from Streptomyces lividans 66 cell-free cultures. The enzyme is a major component of the secreted proteolytic activity. The protease removes only the N-terminal tripeptide from recombinant human GM-CSF and IL-3 but does not cleave recombinant human IL-6. The enzyme cleaves the synthetic tripeptide substrates APA-pNA and APM-pNA but does not cleave substrates with blocked amino terminals. Smaller substrates are not cleaved. The enzyme appears to be a serine protease of 55 kDa molecular weight. The pH optimum is between 7.5 and 8.5 but varies slightly with the substrate. The N-terminal sequence and amino acid composition have been determined.