ISOLATION AND PARTIAL CHARACTERIZATION OF LECTINS FROM INDIAN VARIETIES OF LEGUMINOUS PLANTS.

Lectins are glycoproteins of nonimmune origin derived from plants, microbes, or animal sources. Some plant lectins agglutinate various blood groups of erythrocytes and are therefore called phytohaemagglutinins. In the present study, 21 seeds of Indian variety of plants were used to extract and characterize lectins for their haemagglutination activity against the human ABO blood group antigens. Crude extracts of lectins were prepared using three different extraction methods. From the 21 seed extracts tested, 10 of them showed positive haemagglutination. Rajma (Phaseolus vulgaris var) and kulith (Dolichos biflorus) lectin extracts were used for further characterization. Hapten-inhibition assays using mono and disaccharides showed specificity for N-acetyl galactosamine for rajma lectin extract, whereas kulith lectin did not show any sugar specificity. Partial purification of these extracts by ammonium sulphate fractionation followed by SDS-PAGE showed several protein bands. In haemagglutination assays, kulith lectin extracts showed agglutination only with blood group A, whereas rajma extracts agglutinated RBCs from A, B, and O blood groups. Further, using the kulith extract, negative haemagglutination was observed in two out of nine samples of blood having the A antigen on its membrane. Human blood group A has several subtypes, the major being A1 and A2. It is known that Dolichos biflorus has A1 specific lectins (Nance, 1986; Sharon and Liz., 2004). It is possible that the lectin extracted from the Indian variety of Dolichos biflorus (kulith) is an A1 specific lectin. Purified A1-specific lectin from kulith has the potential to be used for commercial blood typing differentiating A1 from other subtypes of human blood group A.