The Interaction between Chymotrypsin and Horse Leucocyte Neutral Proteinases Inhibitor

Abstract
The inhibition of .alpha.-chymotrypsin by horse leukocyte neutral proteinases inhibitor was time-dependent with synthetic substrate N-benzoyl-L-tyrosine ethyl ester but not with azo-casein. This time dependent could be used to calculate the rate constant Kass for the association of the inhibitor with bovine .alpha.-chymotrypsin (Kass = 0.3 .times. 106 M-1 s-1). The inhibitor reacted with chymotrypsin at a molar ratio of 1:1. The dissociation constant Ki = 0.30 .times. 10-9 M of the complex indicates a very strong interaction between enzyme and inhibitor.