The Purification of Papain by Affinity Chromatography

A water insoluble derivative of a papain inhibitor was prepared by covalently linking Gly-Gly-Tyr(Bzl)-Arg to an agarose resin. The immobilized inhibitor binds active papain specifically. When papain prepared by the method of Kimmel and Smith was activated and applied to a column of the immobilized inhibitor at moderate ionic strength (20 mM EDTA, pH 4.3), about 50% of the total protein was not bound and was found to be catalytically inactive. The bound enzyme was released with distilled water. It contained one mole of SH per mole of protein. When assayed with α-N-benzoyl-l-arginine ethyl ester (25°, pH 6.0) the purified enzyme had a kcat of 28.5 sec-1 and a Km of 18 mM. The specific activity of the purified papain was about twice that of the original preparation and the Km was unchanged. The enzyme, inactivated by an equimolar amount of mercuric chloride could be fully activated even after prolonged storage.