Inhibition of porcine elastase II by chicken ovoinhibitor

Interaction of porcine elastase II with native and modified chicken egg-white ovoinhibitor was studied by determining the residual activity of the partially inhibited enzyme and by direct measurement of the stoichiometry of interaction using affinity chromatography, electrophoresis and gel filtration. It was found that the chymotrypsin binding site that is not modified by mild oxidation with N-chlorosuccinimide (Shechter et al., Biochemistry, (1977) 16, 992-997) is capable of binding elastase II as well. The binding of chymotrypsin and elastase II is mutually exclusive and the affinity of chymotrypsin is stronger. Binding of 2 mol trypsin as 1 mol elastase I by ovoinhibitor does not interfere with the binding of elastase II. There is also an indication that the second binding site for chymotrypsin is capable of forming a complex with an additional molecule of elastase II, but the binding is so weak that it could be detected only by electrophoresis.