Isolation and Characterization of α-Xylose-, α-Galactose-, and α-Mannose-binding Lectins from the Tubers of Arrowhead, Sagittaria trifolia L. var sinensis

Abstract

In the course of survey on biologically active substances in traditional plant foods, we have noted that tubers of arrowhead, Sagittaria trifolia L. var sinensis, contain unique lectins, particularly, specific to α-xylose residues, in addition to α-galactose- and α-mannose residues. Fresh tubers of arrowhead, grown in Suita region, were homogenized in PBS at cold. After separation of starch, the lectin-containing protein fraction was successively fractionated by using affinity columns, each lectin being further purified by gel filtration. The molecular properties and binding specificities of these lectins were characterized; α-xylose-specific lectin, first found in plant kingdoms, is a glycoprotein with molecular mass 5×10⁴, consisting of two subunits, 26 kDa. It binds to terminal α-xylose residue of xyloglucans. Possiblly, it may also recognize terminal β-xylose residue. α-galactose-specific lectin is also glycoprotein, molecular mass 5.2×10⁴, with two subunits, 26 kDa. This lectin binds to terminal α-galactose residues of galactomannans, also with human blood B substance. α-Mannose-specific lectin, is a dimeric protein with subunit of 26 kDa. It recognized terminal α-mannose of yeast mannans and glycoconjugates, In addition, it also recognizes terminal α-d-arabinofuranose residues.