Novel propeptin analog, propeptin-2, missing two amino acid residues from the propeptin C-terminus loses antibiotic potency.

A novel inhibitor of prolyl endopeptidase, the propeptin analog propeptin-2 (C105H130N24O(24)), missing two amino acid residues from the propeptin C-terminus was isolated from the fermentation broth of propeptin-producing Microbispora sp. SNA-115 grown using a large inoculum. It shows the same enzyme inhibition activity as propeptin against prolyl endopeptidase (Ki=1.5 microM), but its antimicrobial activity against Mycobacterium phlei is more than 100-fold lower.