Inhibits subtilisin-type microbial serine proteases incuding proteinase K, subtilisin BPN', subtilisin Carlsberg and subtilisin E in a non-stoichiometric manner. Weakly inhibits A.oryzae protease and some metalloproteases including pronase E. Does not inhibit trypsin, chymotrypsin, S.griseus alkaline protease or A.lyticus lysyl endopeptidase. CLSI-II has a wider inhibitory specificity than CLSI-III. Forms active dimers on storage in aqueous solution, possibly through formation of an intermolecular disulfide bond. The N-terminal Asn is removed in about 50% of both the CLSI-II and CLSI-III chains. Belongs to the protease inhibitor I3 (leguminous Kunitz-type inhibitor) family.