Purification and some properties of two proteinase inhibitors from Erythrina acanthocarpa seed

Two proteinase inhibitors (DE-1 and DE-2) were purified from Erythrina acanthocarpa seed by gel filtration followed by ion exchange chromatography on DEAE-cellulose and DEAE-sepharose. They contain 163-164 amino acids (molecular weight 18000) including four half-cystine residues and resemble the Kunitz-type proteinase inhibitors. The N-terminal amino acid sequence of DE-1 also shows homology with those of the Kunitz-type inhibitors. For DE-2 no free N-terminal amino acid was found. DE-1 contains a potent inhibitor for both porcine trypsin and bovine alpha-chymotrypsin. Inhibitor DE-2 inhibits alpha-chymotrypsin strongly and it has practically no action on trypsin.