Amino acid sequence of a trypsin-chymotrypsin inhibitor, B-III, of peanut (Arachis hypogaea).

The amino acid sequence of peanut trypsin-chymotrypsin inhibitor, B-III, was determined by conventional methods. The limited proteolysis of B-III with trypsin indicated the reactive sites of B-III for trypsin to be Arg(10)-Arg(11) and Arg(38)-Ser(39). Comparison of the established sequence of B-III with those of other Bowman-Birk type double-headed protease inhibitors indicated that B-III has four amino acid insertions and one amino acid deletion. It is especially interesting that the amino acid residue in the P1' position (No. 11) of the first reactive site for trypsin is arginine instead of serine, which seems to be conserved at the P1' position of the reactive sites of all Bowman-Birk type protease inhibitors.