Purification and Properties of Two Protease Inhibitors from Rat Skin Inhibiting Papain and Other SH-Proteases.

Abstract

Two papain [EC 3.4.22.2] inhibitors, I1 and I2, from rat skin extract were purified by affinity chromatography on KSCN-modified papain-agarose gel and by gel filtration on Sephadex G-100. I1 had a MW of 74,000, a pI of 4.6 and contained 4% carbohydrates. I1 inhibited papain, ficin, bromelain, rat skin benzoylarginine-2-naphthylamide hydrolase and to a minor extent, rat skin cathepsin C [EC 3.4.14.1] and bovine trypsin. Bovine chymotrypsin or rat skin cathepsin D were not inhibited and benzoylarginine-2-naphthylamide hydrolase was inhibited only at alkaline pH. An inhibitor corresponding to I1 was present in various rat tissues and also in serum. A similar inhibitor was present in the skin of cat, rabbit, guinea pig and man. I2 had a MW of 13,400, a pI of 4.9 and it contained no carbohydrates. I2 inhibited all thiol proteases tested, but not trypsin, chymotrypsin or rat skin cathepsin D. I2 formed an equimolar complex with papain and benzoylarginine-2-naphthylamide hydrolase. I2 was present in rat skin, muscle, lung and small intestine, but not in kidney, liver or serum. A similar inhibitor was found in skin extracts of cat, rabbit, guinea pig and man.