K-26, a novel inhibitor of angiotensin I converting enzyme produced by an actinomycete K-26.

A novel inhibitor of angiotensin I converting enzyme (ACE), designated K-26, was isolated from the broth filtrate of an actiomycete K-26. K-26 is a water soluble, acidic peptide composed of an equal mol of L-isoleucine, L-tyrosine and 1(R)-1-amino-2-(4-hydroxyphenyl)-ethylphosphonic acid. The IC50 of K-26 for ACE inhibition was 6.7 ng/ml when hippuryl-L-histidyl-L-leucine was used as a substrate of ACE. K-26 possesses hypotensive activity in vivo.