Belactins A and B, new serine carboxypeptidase inhibitors produced by Actinomycete. I. Taxonomy, production, isolation and biological activities.

Belactins A and B, new inhibitors of serine carboxypeptidase were discovered in the fermentation broth of Saccharopolyspora sp. MK19-42F6. They were purified by ethyl acetate extraction, silica gel chromatography, Sephadex LH20 chromatography, Capcellpak C18 SG120 reversed phase HPLC and centrifugal partition chromatography (CPC) following their inhibitory activity against carboxypeptidase Y (CP-Y). The inhibition constants (K-i) of belactins A and B against CP-Y are 0.14 and 0.27 mu M respectively. Belactins A and B have highly specific inhibitory activities for CP-Y among various peptidases, have no antimicrobial activities at 100 mu g/ml and have low toxicities.