Physicochemical properties of intermediary subunits of broad bean 11S globulin.

Three intermediary subunits of legumin, IS-I, IS-II and IS-III, were isolated. They were characterized by means of electrophoresis, amino acid and NH2-terminal sequence analyses. Reconstitution of pseudolegumin was carried out and the yield of 11S-size product from either IS-II or IS-III was more than 95%, while IS-I almost formed a 9S-size product and a small amount of 11S-size product. The pseudolegumins were similar to the native legumin in terms of their secondary structure. The products from IS-I and IS-II formed a stronger gel than the native legumin upon heating, but that from IS-III failed to form a self-supporting gel. IS-I plays an important role in increasing the gel hardness of legumin.