Isolation and properties of complexes of the Bowman-Birk soybean inhibitor with trypsin and chymotrypsin.

Complexes of the Bowman-Birk soybean inhibitor with either trypsin or chymotrypsin and with both of these enzymes were isolated by gel atration. Amino acid analyses and molecular weight estimates by gel filtration were consistent with the formation of a 1: 1 molar complex between inhibitor and trypsin or chymotrypsin and a 1: 1: 1 molar complex composed of inhibitor, trypsin, and chymotrypsin. The binary complexes were also isolated by aflinity chromatography employing insoluble derivatives of trypsin and chymotrypsin. Determination of the residual enzymic activity in solutions of the isolated complexes permitted an evaluation of their dissociation constants.