Studies on the Function of Disulfide Bond Cys(112)-Cys(115) in Arrowhead Proteinase Inhibitors.

Two cysteine residues which compose the disulfide bond Cys(112)-Cys(115) in the arrowhead inhibitor were replaced by Ala and Ser respectively, using site-directed mutagenesis. The mutant has similar inhibitory activities as that of the wild type. The result suggests that the disulfide bond of Cys(112)-Cys(115) in the arrowhead inhibitor is not indispensable to its inhibitory activity.