The Amino Acid Sequence of a Bowman-Birk Type Proteinase Inhibitor from Faba Beans (Vicia faba L.)

Abstract

The amino acid sequence of a Bowman-Birk type proteinase inhibitor (FBI) from seeds of faba bean (Vicia faba L.) was determined by analysis of peptide fragments generated by reduction and S-carboxymethylation of enzymatically modified inhibitors, which were obtained from native FBI by limited proteolysis with TPCK-trypsin or TLCK-chymotryp-sin at pH 3.5. The established sequence showed that FBI is highly homologous with Vicia angustifolia inhibitor (VAI) but lacks the portion corresponding to the C-terminal 9 amino acids of VAI. The trypsin reactive-site peptide bond in FBI was also indicated to be Lys(16)-Ser(17) and the chymotrypsin reactive-site peptide bond to be Tyr(42)-Ser(43) by limited proteolysis with TPCK-trypsin or TLCK-chymotrypsin and by sequence compari-son with other Bowman-Birk type inhibitors.