Action of papain on human serum globulins.

Studies on the degradation of animal and human serum antibody type proteins by various proteolytic enzymes have indicated that molecules of approximately one-half and one-quarter the size of the parent 160,000-molecular weight protein may be readily formed (l-5). Porter (6) has recently shown that rabbit y-globulin is degraded by papain into fragments of the above size range and has separated such digests into three discrete fractions by chromatography on carboxymethyl-cellulose columns. With papain under conditions in which normal y,-globulins (7) are only partially degraded into lower molecular weight fragments, it has been found that all myeloma serum globulins examined are uniformly converted to molecules sedimenting near 3.5 S. This is in the range of the most commonly reported values for Bence-Jones proteins (8). Under analogous conditions, macroglobulins of the Waldenstrom type (9) are partially converted by papain to molecules sedimenting at this rate. The present studies are concerned with the properties of the products formed in the splitting of several human globulins by papain, with special reference to the myeloma proteins.