Abstract
The Gln-Val-Val-Ala-Gly sequence occurs frequently in several thiol proteinase inhibitors, suggesting that this conserved sequence may be one of the reactive sites in the inhibitors. In order to study the effects of the sequence on thiol proteinases, we synthesized H-Gln-Val-Val-Ala-Gly-OH (VI) and its related peptide derivatives by the conventional solution method and examined their effects on the enzymatic activity of papain. We found that Z-Gln-Val-Val-Ala-Gly-OMe (IV) not only inhibits papain but also protects it from T-kininogen, which is one of thiol proteinase inhibitors. Apparently this peptide (IV) binds with some part of papain in competition with T-kininogen.
