Lectinochemical studies on the affinity of Anguilla anguilla agglutinin for mammalian glycotopes.

Abstract Anguilla anguilla agglutinin (AAA) is a fucose-specific lectin found in the serum of the fresh water eel. It is suggested to be associated with innate immunity by recognizing disease-associated cell surface glycans, and has been widely used as a reagent in hematology and glycobiology. In order to gain a better understanding of AAA for further applications, it is necessary to elucidate its binding profile with mammalian glycotopes. We, therefore, analyzed the detailed carbohydrate specificity of AAA by enzyme-linked lectinosorbent assay (ELLSA) with our extended glycan/ligand collection and lectin-glycan inhibition assay. Among the glycans tested, AAA reacted well with nearly all human blood group A h (GalNAcα1→3[ l Fucα1→2]Gal), B h (Galα1→3[ l Fucα1→2]Gal) , H l Fucα1→2Gal) and Le b (Fucα1→2Galβ1→3[Fucα1→4]GlcNAc) active glycoproteins (gps), but not with blood group Le a (Galβ1→3[Fucα1→4]GlcNAc) substances, suggesting that residues and optimal density of α1-2 linked l Fuc to Gal at the non-reducing end of glycoprotein ligands are essential for lectin-carbohydrate interactions. Blood group precursors, Galβ1-3GalNAc ( T ), GalNAcα1-Ser/Thr ( Tn ) containing glycoproteins and N -linked plasma gps, gave only negligible affinity. Among the mammalian glycotopes tested, A h , B h and H determinants were the best, being about 5 to 6.7 times more active than l Fuc, but were weaker than p -nitrophenylαFuc indicating that hydrophobic environment surrounding the l Fuc moiety enhance the reactivity. The hierarchy of potency of oligo- and monosaccharides can be ranked as follows: p -nitrophenyl-αFuc > A h , B h and H > l Fuc > l Fucα1→2Galβ1→4Glc (2′-FL) and Galβ1→4[ l Fucα1→3]Glc (3′-FL), while LNDFH I ( Le b hexa-), Le a , Le x (Galβ1→4[Fucα1→3]GlcNAc), and LDFT (gluco-analogue of Le y ) were inactive. From the present observations, it can be concluded that the combining site of AAA should be a small cavity-type capable of recognizing mainly H /crypto H and of binding to specific polyvalent ABH and Le b glycotopes.