Carbohydrate Binding Specificity of a Beetle (Allomyrina dichotoma) Lectin1

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Abstract
Carbohydrate binding specificity of a lectin, allo A, isolated from a beetle (Allomyrina dichotoma), was investigated by means of lectin affinity chromatography. Sialylated complex-type and hybrid-type oligosaccharides/glycopeptides, and sialyllactose were retained by the column, whereas desialylated ones were retarded but not retained by the column. The association constants of allo A for biantennary oligosaccharides from human serum transferrin, determined by frontal analysis, were 8.0 × 105 M−1, 4.5 × 105 M−1, and 2.5 × 105 M−1 for disialo-, monosialo-, and asialo-oligosaccharides, respectively. Removal of the β-galactose residues markedly reduced the association constant to 3.5 × 103 M−1 Furthermore, allo A was found to have no affinity for mucin-type glycopeptides carrying the sialylated Gal.β1→3 Ga1NAc sugar sequence (Ka: 3.5 × 103 M−1). The results of this study indicated that allo A strongly binds to the trisaccharide structure, NeuAcα2–3(6)Gal, β1–4G1cNAc, and that its binding potency is affected by the inner core structures of oligosaccharides and glycopeptides, because the presence of a bisecting N-acetyl-glucosamine residue and an a-fucose residue linked to the innermost N-acetylglucosamine residue reduced the association constants for oligosaccharides and glycopeptides.