Proteolytic enzymes: electrophilic participation in the acylation step

Abstract

Acylation of α-trypsin and purified fractions of stem-bromelain by substituted phenyl ester substrates has a low sensitivity to Hammett σ consistent with the involvement of an electrophilic interaction with the ether oxygen. General-base assisted thiol attack is shown to be a minor route in acylation of thiol proteases. Stem bromelain's heterogeneity is confirmed and a fractionation procedure is reported for isolation of macro-quantities of the constituent enzymes.