Putative “acylaminoacyl” peptidases from Streptomyces griseus and S. coelicolor display “aminopeptidase” activities with distinct substrate specificities and sensitivities to reducing reagent

Aminopeptidases from Streptomyces griseus (SGRAP) and S. coelicolor (SCOAP) were cloned and characterized to clarify their biochemical characteristics. Although both enzymes had been annotated as putative oligopeptidases of family S9 enzymes, they showed “aminopeptidase” activities, not “oligopeptidase” activities. Although their deduced amino acid sequences showed high similarity (69% overall sequence homology), they showed distinct substrate specificities and sensitivities to the reducing reagent dithiothreitol (DTT). The reaction pH and addition of DTT dramatically affected the substrate preference of SGRAP. Furthermore, SCOAP selectively hydrolyzed phenyalanine p-nitroanilide (Phe-pNA) in the presence or absence of DTT. The chimera protein between SGRAP and SCOAP was constructed to identify the region responsible for the properties described above. Furthermore, Cys409 of SCOAP was identified as a functional residue responsible for activation by reducing reagent DTT.