[Interaction of trypsin with a trypsin inhibitor from bovine colostrum]

Kinetics of trypsin association with trypsin inhibitor from colostrum (IC) was studied. The association rate constant is 3-10-5 M- minus 1 sec- minus 1 at pH 7,8, 25 degrees C. The rate constant for the complex dissociation was determined from the kinetics of the IC displacement from the complex with trypsin by a specific substrate and was found to be 5-10- minus 6 sec- minus 1 (pH 7,8; 25 degrees C). The equilibrium constant (Ki) was measured in a special experiment and was equal to 4-10- minus 12 M (p H 7,8; 25 degrees C). The similarity of this reaction and the association of trypsin with other protein inhibitors was discussed.