Abstract
Fruit bromelain [EC 3. 4. 4. 24] cleaved human IgG into two kinds of fragments separable by CM- and DEAF-cellulose column chromatography. The resulting fragments, Fab(F) and Fc(F), apparently resembled those obtained using papain [EC 3. 4. 4. 10] as regards antigenicity, electrophoretic mobility, sedimentation constant, molecular weight, and amino acid composition. Fab(F) and Fc(F) had sedimentation constants of 3.7S and 3.5S, respectively. Fab(F) was shown by gel filtration to have a molecular weight of 51, 000 and Fc(F) a molecular weight of 48, 000. These results suggest that the possible site of fruit bromelain cleavage of human IgG could be very close to that of papain.
Studies of the cleavage by fruit bromelain of human IgG at different enzymesubstrate ratios and digestion times showed that human IgG has a stronger resistance to fruit bromelain than to papain. By experiments on subclass specificity, it was shown that this difference in resistance to enzymatic attack was mainly due to the difference in the nature of the enzyme-resistant subclass. Thus, the fruit bromelainresistant component involves IgG 1 and IgG 2, whereas it has been shown that the papain-resistant component involves only IgG 2.
