FURTHER CHARACTERIZATION OF THE BINDING-PROPERTIES OF A GALNAC SPECIFIC LECTIN FROM CODIUM FRAGILE SUBSPECIES TOMENTOSOIDES

Previous study on the binding properties of a lectin isolated from Cod ium fr agile subspecies tomentosoides (CFT) indicates that this lectin recognizes the GalNAc alpha 1--> sequence at both reducing and nonred ucing ends, In this study, the carbohydrate specificity of CFT was fur ther characterized by quantitative precipitin (QPA) and inhibition of lectin-enzyme binding assays, Of the glycoforms tested for QPA, all as ialo-GalNAc alpha 1--> containing glycoproteins reacted well with the lectin, Asialo hamster and ovine submandibular glycoproteins, which co ntain almost exclusively Tn (GalNAca alpha 1-->Ser/Thr) residues as ca rbohydrate side chains, and Streptococcus type C polysaccharide comple tely precipitated the lectin added, while the GalNAc beta 1-->containi ng Tamm-Horsfall Sd(a(+)) glycoprotein and its asialo product were ina ctive, Among the oligosaccharides tested for inhibiting lectin-glycopr otein interaction, GalNAc alpha 1-->3GalNAc beta 1-->3Gal alpha 1-->4G al beta 1--> 4Glc(Fp) and Gal beta 1-->3GalNAc alpha 1-->benzyl (T alp ha) were the best, and about 125-fold more active than GalNAc, They we re about 3.3, 6.6, and 43 times more active than Tn containing glycope ptides, GalNAc alpha 1-->3(LFuc alpha 1--> 2)Gal(A(h)) and Gal beta 1- ->3GalNAc(T), respectively, From the present and previous results, it is concluded that the combining site of CFT is probably of a groove ty pe that recognizes from GalNAc alpha l--> to pentasaccharide(Fp). The carbohydrate specificity of this lectin can be constructed and summari zed in decreasing order by lectin determinants as follows: Fp and T al pha > Tn cluster > A(h) >> I/II.