Purification of a sialic acid-specific lectin from the Indian scorpion Heterometrus granulomanus.

A sialic acid-specific lectin, scorpin, has been purified to apparent homogeneity from the Indian scorpion Heterometrus granulomanus by affinity chromatography on equine submandibular gland glycopeptides linked to Sepharose and gel filtration on Sephadex G-200. The lectin has a molecular mass of 500 000 Da and was dissociated into single polypeptide chains of 15 000 Da, as determined by SDS gel electrophoresis in the presence of 2-mercaptoethanol. Scorpin is a glycoprotein containing 2.8% sugars. Its specificity was investigated by the inhibition of hemagglutination with various derivatives of sialic acid and other sugars. N-Acetylneuraminic acid gave better inhibition than N-glycoloylneuraminic acid but showed less inhibitory effect than sialyl-alpha(2----3)-lactose and disialyllactose. Among the sialoglycoconjugates tested, equine submandibular gland glycopeptide was found to be the most potent inhibitor. Scorpin showed a strong tendency to bind to carboxyl groups, since reduction of the carboxyl group of N-acetylneuraminic acid destroyed the inhibitory potency of this sugar. Furthermore, D-glucuronic acid inhibited hemagglutination whereas N-acetylglucosamine or N-acetylgalactosamine were not inhibitors.