Isolation and characterization of a sialic acid-specific binding lectin from the hemolymph of Asian horseshoe crab, Tachypleus tridentatus.

A lectin was isolated from the hemolymph of Asian horseshoe crab Tachypleus tridentatus by using glycophorin HA affinity chromatography and Sephacryl S-300 gel filtration. The lectin's molecular weight was approx. 533 kDa; being a simple protein comprised of two non-identical subunits with molecular weights of 30 and 32 kDa. The hemagglutinating activity of the lectin against equine erythrocytes was strongly inhibited by several sialoglycoproteins and weakly inhibited by sialic acid, although not inhibited by neutral sugars, hexosamines, N-acetylhexosamines, glucuronic acid, or several asialoglycoproteins. In addition, glycophorin HA was more effective than glycophorin HA digested with trypsin in inhibiting hemagglutination of the lectin. These results suggest that the purified lectin specifically reacts with sialic acids containing glycoprotein.