Purification and some properties of a proteinase inhibitor (DE-1) from Peltophorum africanum (weeping wattle) seed.

A proteinase inhibitor (DE-1) from the seed of Peltophorum africanum (Weeping wattle) was purified by chromatographic procedures involving Sephadex G-50, DEAE-cellulose and DEAE-Sepharose. It comprises 162 amino acid residues (molecular mass 18 000 Da) including 4 half-cystine residues and resembles the Kunitz-type proteinase inhibitors. The N-terminal primary structure of DE-1 showed homology with Kunitz soybean trypsin inhibitor and also with the proteinase inhibitors from Albizzia julibrissin and Erythrina latissima seeds. The inhibitor stoichiometrically inhibited trypsin and also alpha-chymotrypsin in the molar ratio of 1:1 and represents, therefore, a Kunitz-type double-headed proteinase inhibitor.