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 (C 105 H 130 N 24 O 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 μM), but its antimicrobial activity against Mycobacterium phlei is more than 100-fold lower.