Acridine dyes as effectors in papain catalysis

Abstract

The catalytic activity of the sulfhydryl protease, papain, toward the synthetic ester substrate, α- N-benzoyl- l-arginine ethyl ester, is enhanced by several acridine dyes. Kinetic studies on the effects of proflavine (3,6-diaminoacridine) on the papain-catalyzed hydrolysis at pH 6.6 (25 °C) of both α- N-benzoyl- l-arginine ethyl ester and N-benzoylglycine ethyl ester indicate that the dye primarily affects K m(app) , having little or no effect upon k ca t. On the other hand, proflavine appears to have no measurable effect upon the catalytic activity of papain toward N-benzyloxycarbonylglycine p-nitrophenyl ester. Quinacrine hydrochloride appears to behave much like proflavine in theenhancement of papain-catalyzedbenzoylarginine ethyl ester hydrolysis. These findings are interpreted in terms of possible effects of dye on individual rate constants in the “acyl enzyme” scheme which characterizes papain action, and they are compared with reported findings concerning the rate-enhancing effects of proflavine on the related sulfhydryl protease ficin.