Muraceins--muramyl peptides produced by Nocardia orientalis as angiotensin-converting enzyme inhibitors. I. Taxonomy, fermentation and biological properties.

Three muraceins , a family of muramyl peptides, were isolated from Nocardia orientalis as inhibitors of angiotensin-converting enzyme (ACE). Muracein A, the most potent inhibitor, inhibited ACE competitively with a Ki of 1.5 microM. Liver alcohol dehydrogenase and carboxypeptidase A, two other zinc-containing enzymes, were not inhibited at 150 microM. Inhibition of ACE could not be reversed by divalent cations.