19F nuclear magnetic resonance studies of the interaction of inhibitors with chymotrypsin. Derivatives of tryptophan and phenylalanine

Abstract

The binding of the inhibitors N-trifluoroacetyltryptophan, N- trifluoroacetylphenylalanine, N-acetyl-tryptophan and N- acetylphenylalanine to chymotrypsin has been studied by 19F N.M.R. spectroscopy at several pH values. Methods for determining the binding parameters, KI and ΔB, including a model for enzyme oligomerization and competitive inhibition from a second inhibitor, are discussed and a general non-linear least-squares method is presented. Values of KI and ΔB are recorded for D and L enantiomers of tryptophan derivatives and for D-phenylalanine derivatives. The results are discussed in terms of a model for the aromatic binding site of chymotrypsin.