Carbohydrate specificity of an agglutinin isolated from the root of Trichosanthes kirilowii

The root of Trichosanthes kirilowii, which has been used as Chinese folk me dicine for more than two thousand years, contains a Gal specific lectin (TK A). In order to elucidate its binding roles, the carbohydrate specificities of TKA were studied by enzyme linked lectinosorbent assay (ELLSA) and by i nhibition of lectin-glycoform binding. Among glycoproteins (gp) tested, TKA reacted strongly with complex carbohydrates with Gal beta 1-->4GlcNAc clus ters as internal or core structures (human blood group ABH active glycoprot eins from human ovarian cyst fluids, hog gastric mucin, and fetuin), porcin e salivary glycoprotein and its asialo product, but it was inactive with he parin and mannan (negative control). Of the sugar inhibitors tested for inh ibition of binding, Neu5Ac alpha 2-->3/6Gal beta 1-->4Glc was the best and about 4, 14.6 and 27.7 times more active than Gal beta 1-->4GlcNAc(II), Gal beta 1-->3GalNAc(T) and Gal, respectively. From these results, it is sugge sted that this agglutinin is specific for terminal or internal polyvalent G al beta 1-->4GlcNAc beta 1-->, terminal Neu5Ac alpha 2-->3/6Gal beta 1-->4G lc and cluster forms of Gal beta 1-->3GalNAc alpha residues. The unusual af finity of TKA for terminal and internal Gal beta 1--> glycotopes may be use d to explain the possible attachment roles of this agglutinin in this folk medicine to target cells.