The Reactivity of Nucleophilic Reagents with Furoyl-chymotrypsin

This report is the second of two papers dealing with the effect of structure on reactivity in a single, defined step of a chymotrypsin-catalyzed reaction. A previous study of the rates of hydrolysis of a series of substituted benzoyl-chymotrypsins provided evidence for a significant amount of participation of basic or nucleophilic groups in the reaction (l), a conclusion which was reached independently by Bender and Nakamura from a study of the rates of acyl-enzyme formation from a series of substituted phenyl esters (2). The present study was carried out to determine the effect of structure on the reactivity of a series of nucleophilic reagents toward an acyl-chymotrypsin, in the hope that the results would shed some light on the role played by the enzyme in activating the nucleophilic reagent or the acyl group or both for react,ion. It is well known that many alcohols and amines react with acyl-chymotrypsins and there is scattered quantitative data in the literature (3-10). The studies described here were carried out with furoyl-chymotrypsin (1, 3) which is similar to the cinnamoyl-chymotrypsin studied by Bender, Schonbaum, and Zerner (11, 12) in that it undergoes an easily measurable spectral change on reaction, which facilitates rate measurements.