Catfish (Clarias batrachus) serum lectin recognizes polyvalent Tn [α-d-GalpNAc1-Ser/Thr], Tα [β-d-Galp-(1→3)-α-d-GalpNAc1-Ser/Thr], and II [β-d-Galp(1→4)-β-d-GlcpNAc1-] mammalian glycotopes Original Research Article

A new calcium dependent GalNAc/Gal specific lectin was isolated from the serum of Indian catfish, Clarias batrachus and designated as C. batrachus lectin (CBL). It is a disulfide-linked homodecameric lectin of 74.65 kDa subunits and the oligomeric form is essential for its activity. Binding specificity of CBL was investigated by enzyme-linked lectin-sorbent assay using a series of simple sugars, polysaccharides, and glycoproteins. GalNAc was more potent inhibitor than Gal; and α glycosides of both were more inhibitory than their β counterparts. CBL showed maximum affinity for human tumor-associated Tn-antigens (GalNAcα1-Ser/Thr) at the molecular level and was 3.5 times higher than GalNAc. CBL interacted strongly with polyvalent Tn and Tα (Galβ1,3GalNAcα1-) as well as multivalent-II (Galβ1,4GlcNAcβ1-) antigens containing glycoproteins and intensity of inhibition was 103–105 times more than monovalent ones. The overall specificity of CBL lies in the order of polyvalent Tn, Tα and II ≫≫ monovalent Tn ⩾ Me-αGalNAc > monovalent Tα > Me-βGalNAc > Me-αGal > monovalent T > GalNAc > monovalent F > monovalent II > Me-βGal > Gal.