A lectin from the Asian horseshoe crab Tachypleus tridentatus: purification, specificity and interaction with tumour cells.

A lectin from the haemolymph of the Asian horseshoe crab Tachypleus tridentatus was purified to homogeneity by affinity chromatography on Sepharose 4B-bound N-acetylneuraminic acid. The specificity of this lectin was studied by haemagglutination inhibition with sialic acid analogues, N-acetylhexosamines and glycoproteins. For the interaction with the agglutinin the N-acetyl group and the glyceryl side chain of N-acetylneuraminic acid are important, while presence of an aglycon, specially an alpha-glycosidically linked lactose increases affinity to the lectin. The strongest glycoprotein inhibitors were ovine as well as bovine submaxillary mucin and Collocalia mucin, all being O-chain glycoproteins but carrying completely different carbohydrate chains. The majority of N-chain proteins were inactive. As the lectin agglutinates human erythrocytes, but not the murine lymphoma lines Eb and ESb or the human colon carcinoma HT 29, these cancer cells apparently lack the 'Tachypleus tridentatus agglutinin-receptor' which is present on red cells and O-chain glycoproteins.