Propeptin is a metabolite of Microbispora sp. SNA 115, a peptide antibiotic composed of 19 amino acids. Propeptin has weaker activity against Pseudomonas aeruginosa, Mycobacterium monobacterium, and Xanthomonas oryzae. It has no effect on KB and L1210 cells of tumor cell lines, but has an inhibitory effect on prolyl endopeptidase.