Inhibition of α-Chymotrypsin by Suc-L-Tyr-D-Leu-D-Phe-pNA, a Stereoisomer of a Specific Substrate

Stereoisomers of specific chromogenic substrates for various enzymes were synthesized by a conventional solution method. Among them, Suc-L-Tyr-D-Leu-D-Phe-pNA was found to be an effective and specific inhibitor of α-chymotrypsin. However, Suc-L-Tyr-D-Leu-D-Phe-Pipe did not show any inhibitory effect on α-chymotrypsin. The role of the pNA moiety of the above stereoisomer was investigated, and it was found that the pNA moiety participated in binding with some part of the enzyme, resulting in the manifestation of the inhibitory activity.