Amastatin is a oligopeptide antibiotic complex that is a competitive inhibitor of aminopeptidases and also has antitumor property.
Amastatin was isolated from the culture filtrate of Streptomyces spME98-M31.
Epiamastatin is a diastereoepimer of the effective peptidase inhibitor amastatin and differs structurally by a single transposition of the OH group with H atom at C2. Compared with amastatin, epiamastatin is pharmacologically inactive. 
clipped from: bio-synthesis.blogspot.com