Studies on the proteolytic activity of γ-globulin preparations

Abstract

The proteolytic activities of several [gamma]-globulin preparations were tested. These included sulphate-precipitated human and bovine preparations and human and bovine Cohn fraction II preparations as well as purified [gamma]-globulin preparations. Up to 14mg. of diffusible peptides and glycopeptides/g. of [gamma]-globulin was liberated after dialysis and up to 10mg. of peptides/g. after incubation and trichloroacetic acid precipitation, as products of the degradation process in incubated [gamma]-globulin. e-Aminohexanoic acid and p-chloromercuribenzoic acid, as well as heating at 60[degree] for 40 min., were shown to inhibit strongly these proteolytic activities. Streptokinase was shown to activate strongly the proteolytic activity of all the human preparations (sulphate-precipitated, Cohn fraction n, and purified [gamma]-globulin. Two distinct pH optima were shown for human and bovine [gamma]-globulin preparations: one at pH 8, the other at pH 3.8 (the latter activity could be demonstrated only in the presence of cysteine). Both 131I-labelled human Cohn fraction II and bovine fibrinogen were attacked by a sulphate-precipitated preparation of [gamma]-globulin. Of the synthetic substrates tested toluene-p-sulphonyl-L-arginine methyl ester was hydrolysed by both the sulphate-pre-cipitated and Cohn fraction II preparations, as was benzoyl- L-arginine amide at pH 5, but only in the presence of cysteine, These data are interpreted to indicate that at least two enzymes are present in [gamma] -globulin preparations, one being similar to the plasmin system, the other similar to cathepsin B.