Heterogeneity of mouse myeloma gamma G globulins as revealed by enzymatic proteolysis.

The sensitivity of mouse myeloma γG globulins to enzymatic proteolysis has been investigated under several experimental conditions. γG1 was found to be more resistant to papain or tryptic cleavage than γG2d and γG2b. Minor differences were found between the reactivities of the latter two proteins. γG2b showed extremely high sensitivity to the action of pepsin. The addition of cysteine to the incubation mixtures of globulins with papain or trypsin enhanced the degree of fragmentation, but some physical and immunochemical properties of these fragments were found to be different from those of fragments obtained in the absence of cysteine. The possible role of this reducing agent has been discussed.