Novel Epoxysuccinyl Peptides. Selective Inhibitors of Cathepsin B, in Vitro

A series of new epoxysuccinyl peptides were designed and synthesized to develop a specific inhibitor of cathepsin B. Of these compounds, N-(L-3-trans-ethoxycarbonyloxirane-2-carbonyl)-L-isoleucyl-L-proli ne (compound CA-030) and N-(L-3-trans-propylcarbamoyloxirane-2-carbonyl)-L-isoleucyl-L-prol ine (compound CA-074) were the most potent and specific inhibitors of cathepsin B in vitro. The carboxyl group of proline and the ethyl ester group or the n-propylamide group in the oxirane ring were necessary, the ethyl ester group or the n-propylamide group being particularly effective for distinguishing cathepsin B from other cysteine proteinases such as cathepsins L and H, and calpains.