Limited Proteolysis of Soybean Beta-conglycinin

The tryptic digestion of beta-conglycinin was studied by the pH-stat method and sodium dodecyl sulfate gel electrophoresis. The proteolysis of the protein was not affected by the change of ionic strength. This property was distinct from that of glycinin which is degraded rapidly at a low ionic strength.

Five stable fragments were generated in the degradation course. Two kinds of beta-conglycinin, one of which consisted of only the beta-subunit and the other of only the alpha’ and alpha-subunit, were isolated to elucidate the original subunit of the fragments. Two fragments (AT-1 and AT-2) from the alpha’ and alpha-subunit, and three fragments (BT-2-BT-4) from the beta-subunit were generated. The molecular weights of the fragments were similar to those of the glycinin fragments. From the fragment pattern of the beta-subunit, the presence of two types of the beta-subunit was expected.