Immunoglobulin degradation and D-penicillamine action.

Treatment of human IgG with pancreatic elastase gave a product of higher molecular weight than IgG. Its formation was inhibited by blocking IgG sulfhydryl groups with iodoacetamide. Incubation of the high molecular weight product with either glutathione or D-penicillamine yielded Fab- and Fc-like fragments. Addition of oxidized glutathione to mixtures containing either reduced thiol gave a new product of molecular weight intermediate between the high molecular weight product and Fab- and Fc-like fragments. Oxidized D-penicillamine did not substitute for oxidized glutathione. This new product was formed under conditions that favor protein sulfhydryl-disulfide exchange. The effect of D-penicillamine on its formation was discussed in terms of D-penicillamine's mode of action in rheumatoid arthritis.