A novel type of structurally simple nonpeptide inhibitors for α-chymotrypsin. Induced-fit binding of methyl 2-allyl-3-benzene-propanoate to the S2 subsite pocket Original Research Article

Unexpectedly, methyl and benzyl esters of 2-allyl-3-benzenepropanoic acid were found to be not substrates but potent competitive inhibitors for α-chymotrypsin. The inhibitory property of the structurally simple nonpeptidic compounds is ascribed to their high binding affinity to the enzyme at the S2 rather than S1 subsite pocket. These inhibitors exist in a flexible form in solution, but as they bind to the enzyme bulky contrained conformers present in a minute concentration play an important role, forming tighter enzyme·inhibitor complexes by binding to the large hydrophobic S2 pocket. The contrained conformers are thought to be resulted from intramolecular CH/π interactions between a vinylic proton and the aromatic π-electron cloud in the inhibitor molecules. These compounds constitute novel examples of the induced-fit binding inhibitor of possibly simplest structure.