The function of S₁′ subsite pocket of carboxypeptidase A

Our study on the mechanism involved in the substrate recognition of Carboxypeptidase A using transition state analog inhibitors indicated that, on the contrary to the general believe, there is no hydrophobic interaction involved. The bulky hydrophonic moiety entered the narrow opening of the subsite pocket is held by Tyr-248 which moved from the enzyme surface until the catalytic action is over. In the binding of a ligand to Carboxypeptidase A, no hydrophobic interactions appear to be involved between the S₁ ′ subsite and the side chain of the C-terminal amino acid of the ligand. Rather the side chain is held inside the pocket physically by the aromatic ring of Tyr-248.