Use of new synthetic substrates for assays of cathepsin L and cathepsin B.

Efficient methods were developed for synthesizing synthetic substrates for assays of cathepsin B and cathepsin L. Several 2-naphthylamide compounds with a blocked NH2-terminus, Suc-Tyr-Met-NA, beta-Ala-Tyr-Met-NA, and D-Leu-Tyr-Met-NA, were specific and sensitive substrates for cathepsin L and cathepsin B; they were not specific for cathepsin L only, because all of them were also hydrolyzed by cathepsin B. Some kinetic constants for the hydrolyses of these three synthetic substrates by cathepsin B and cathepsin L are given.