DOUBLE-HEADED TRYPSIN CHYMOTRYPSIN INHIBITORS FROM HORSE GRAM (DOLICHOS-BIFLORUS) - PURIFICATION, MOLECULAR AND KINETIC-PROPERTIES/

Four proteinase inhibitors were purified to homogeneity from horse gra m (Dolichos biflorus). These inhibitors are double-headed and inhibit trypsin and chymotrypsin simultaneously and independently. Dissociatio n constants range between 0.87 and 4.6 x 10(-7) M. Each of the four is oinhibitors possesses a crucial lysine residue at the trypsin reactive site. These inhibitors have molecular masses of 8,5 kDa and isoelectr ic points of 4.6 to 5.6. They exist mainly as dimers under physiologic al conditions. Amino acid analysis revealed high levels of half-cystin e, serine, aspartate and proline but low levels of methionine add arom atic amino acids. Amino-terminal sequence analysis revealed that each of the four isoinhibitors have a conserved core sequence but are diver gent at the N-terminal end, These inhibitors belong to the Bowman-Birk (BBI) family of proteinase inhibitors as reflected by their inhibitor y properties, amino acid composition and homology to other BBIs.