Enzymatic and chemical properties of an endopeptidase from the larva of the hornet Vespa crabro.

An endopeptidase from the larvae of the hornet Vespa crabro has been purified to homogeneity. The enzyme has been characterized with respect to molecular weight, amino acid compositon, and amino- and carboxyl-terminal sequences. The catalytic properties of the hornet protease are similar to those of bovine chymotrypsin with respect to inactivation by phenylmethanesulfonyl fluoride and carbobenzoxyphenylalanine chloro ketone and preferential peptide bond cleavage at aromatic amino acid residues. In contrast to bovine chymotrypsin, the hornet protease is not inhibited by the basic pancreatic Kunitz inhibitor, soybean inhibitor, or chicken ovomucoid. The molecular weight, as determined by several independent methods, was found to be 14 500. The protease is a single-chain protein containing two disulfide bonds. The terminal sequences are: NH2-Ile-Val-Gly-Gly-Ile-Asp.....Gly-Lys-Tyr-Pro-Tyr-Gln-Val-Ser-Leu-Arg-COOH.