Purification and properties of the proteinase inhibitors from Erythrina caffra (coast Erythrina) seed.

1. Four proteinase inhibitors (DE-1 to DE-4) were purified from Erythrina caffra seed by gel filtration on Sephadex G-50 followed by ion-exchange chromatography involving DEAE-cellulose and DEAE-sepharose. 2. They comprise 164-166 amino acid residues (mol. wt 18,100) including 4 half-cystine residues and resemble the Kunitz-type proteinase inhibitors. 3. The N-terminal primary structure of DE-3 revealed also homology with those of the Kunitz-type inhibitors. For DE-1, DE-2 and DE-4 no free N-terminal amino acid was found. 4. DE-1 contains a potent inhibitor for both porcine trypsin and bovine alpha-chymotrypsin. Whereas DE-2 inhibits alpha-chymotrypsin strongly and has practically no action on trypsin, DE-3 inhibits both trypsin and alpha-chymotrypsin strongly. DE-4 is a potent inhibitor for trypsin but it binds alpha-chymotrypsin only weakly.