Amino-acid sequences of two basic chymotrypsin inhibitors from silkworm larval hemolymph.

Amino-acid sequences of two basic chymotrypsin inhibitors from silkworm hemolymph (SCI-I and SCI-II) are determined. They are composed of each 62 amino-acid residues with differences in only two positions to each other. They both contain six half cystines in a similar arrangement as that of Kunitz-type proteinase inhibitor, except for the one amino-acid insertion in the first cysteine frame. The inhibitory activity of SCI-II against trypsin should be attributed to Lys44 displacing Gln44 in SCI-I which has no antitryptic activity.