Effect of enzymatic hydrolysis of 7S globulin, a soybean protein, on its allergenicity and identification of its allergenic hydrolyzed fragments using SDS-PAGE

This study was undertaken to investigate the effect of peptic and chymotryptic hydrolyses of 7S globulin, the major allergen of soybean protein, on its allergenicity, as measured by enzyme linked immunosorbent assay (ELISA), and to identify the allergenic hydrolyzed fragments of 7S globulin using SDS-PAGE. When 7S globulin was hydrolyzed by pepsin, the allergenicity was reduced by over 50%. However, the allergenicity of 7S globulin reduced by peptic hydrolysis was recovered in the sera from 5 out of 10 patients following sequential chymotryptic hydrolysis. Two fragments with molecular weights 20-25 and 13-16 kDa, among the hydrolysate of 7S globulin by sequential pepsin and chymotrypsin showed reactivity with sera from 10 soybean-allergenic patients. As a result of the theoretical hydrolyses of beta-conglycinin, which is a major protein of 7S globulin, it is suggested that the 20-25 kDa fragments were the fragments of the alpha-subunit of beta'-conglycinin and that the 10-16 kDa fragments were from the alpha'-subunit.