Hydrolysis of acylchymotrypsins

The hydrolysis rate constant for acylchymotrypsins correlates with the rate constant for reaction of hydroxide ion with the ethyl esters (slope = 0·64, r= 0·867) over a wide range of structure variation in the acyl group. The low sensitivity to change of acyl group and to change in σ for benzoylchymotrypsins (ρ= 1·55, r= 0·952) is suggested to be due to electrophilic participation at the carbonyl oxygen of the acyl group. Tosylchymotrypsin is suggested as a model for the tetrahedral adduct of 4-methylbenzoylchymotrypsin with water and the electrophiles are identified as the NH groups of gly-193, asp-194, and ser-195 peptide bonds.