The Basic Trypsin Inhibitor of Bovine Pancreas VIII. CHANGES IN ACTIVITY FOLLOWING SUBSTITUTION OF REDUCED HALF-CYSTINE RESIDUES

Basic pancreatic trypsin inhibitor with disulfide bond 14-38 reduced by borohydride was reacted with sulfhydryl group reagents. The reduced inhibitor and the dithiobis (Z-nitrobenzoic acid) derivatives retained inhibitory activity toward both trypsin and cr-chymotrypsin. The carboxamidomethyl and aminoethyl derivatives were active toward trypsin but inactive with cu-chymotrypsin. The p-mercuribenzoate and p-mercuribenzenesulfonate derivatives were partially active toward trypsin and inactive toward or-chymotrypsin. The carboxymethyl and N-ethyhnaleimide derivatives were inactive toward both enzymes. The carboxamidomethyl and aminoethyl derivatives inhibited trypsin temporarily and were gradually digested by the enzyme.