Effect of modification of lysine residues of cow colostrum trypsin inhibitor on its antitryptic and antichymotryptic activity

The trypsin inhibitor from cow colostrum belongs to naturally-occurring polyvalent inhibitors. Besides trypsin, to which this inhibitor binds with a ratio of 1: 1 [l] , it also inhibits chymotrypsin to a lesser degree [2]. It is known that the primary structure of inhibitor B from cow colostrum partly resembles that of Kunitz’s basic pancreatic trypsin inhibitor (BPT’I) [3] and that lysine 18 plays a role in the active site of the inhibitor during its binding to trypsin [4] . In this paper, evidence is presented which supports the hypothesis that inhibitor B from cow colostrum has an active site responsible for the inhibition of cY-chymotrypsin different from the active site responsible for the inhibition of trypsin.