Studies on Soybean Trypsin Inhibitors

X. Isolation and Partial Characterization of Four Soybean Double-Headed Proteinase Inhibitors

Abstract

Four Bowman-Birk type double-headed inhibitors (B, C-II, D-II, and E-I) were isolated from soybeans. Inhibitor B was different from Bowman-Birk inhibitor only in chromatographic behaviour. One mole of C-II inhibited one mole each of bovine trypsin and bovine α-chymo-trypsin, probably at the same site, and porcine elastase at another reactive site. In the ordinary assay system D-II and E-I inhibited only trypsin activity at a non-stoichiometric inhibitorenzyme ratio of 1:1.4, and the complexes had rather high dissociation constants. These inhibitors were all inactive toward subtilisin BPN'.