Isolation and characterization of two N-acetyl-D-lactosamine specific lectins from tubers of Arisaema intermedium Blume and A. wallichianum Hook f

Abstract

Two new lectins were purified from the tubers of Arisaema intermedium Blume and A. wallichianum Hook. f. (family: Araceae) by affinity chromatography on asialofetuin-linked amino activated silica beads. The bound lectins were eluted with 0.1 M glycine-HCl, pH 2.5. They gave a single band corresponding to subunit Mr 13.4 kDa in SDS-PAGE, pH 8.3. On gel filtration chromatography, the lectins showed a Mr of 51.2 kDa, suggesting a homotetrameric structure. Both the lectins gave a single peak on size exclusion HPLC and cation-exchange columns and a single band on PAGE, pH 4.5. However, like other monocot lectins, they gave multiple bands in isoelectric focusing and at PAGE 8.3. The lectins were inhibited by N-acetyl-D-lactosamine (LacNAc), a disaccharide and asialofetuin, a complex desialylated serum glycoprotein. They had no requirement for divalent metal ions i.e., Ca²⁺ and Mn²⁺ for their activity and were found to be mitogenic towards human lymphocytes. A. intermedium showed antiproliferative effect against various human cancer cell lines in vitro.