INHIBITION OF EXOGENOUS SERINE PROTEINASES BY AN INHIBITOR OF TRYPSINFROM BUCKWHEAT SEEDS (IT-1)

The inhibition of exogenous trypsin- and alpha-chymotrypsin-like prote inases by a proteinase inhibitor from buckwheat seeds (IT-1) has been studied. The inhibition constants for bovine trypsin and alpha-chymotr ypsin and human granulocyte cathepsin G are 1.1, 67, and 200 nM, respe ctively. The specificity of IT-1 with regard to its primary sequence a t the active site and to its homology with inhibitors of the potato in hibitor I family has been analyzed. It is concluded that IT-1 cannot b ind human granulocyte elastase by virtue of the basic nature of the P- 1 (Arg) residue in the active site.