2 LECTINS FROM THE MARINE SPONGE HALICHONDRIA-OKADAI - AN N-ACETYL-SUGAR-SPECIFIC LECTIN (HOL-I) AND AN N-ACETYLLACTOSAMINE-SPECIFIC LECTIN(HOL-II)

Two lectins (HOL-I and HOL-II) were isolated from the marine sponge Ha lichondria okadai by affinity chromatography on a bovine submaxillary mucin (BSM)-Toyopearl and an acid-treated Sepharose 4B columns, respec tively. In hemagglutination inhibition assays, GlcNAc, GalNAc, and the ir methyl glycosides were the most potent inhibitors among the monosac charides tested against the HOL-I-mediated hemagglutination, suggestin g that HOL-I can especially recognize the N-acetyl groups of the sugar s. This N-acetyl specificity was supported by H-1 NMR analyses; the hi ghest field-shifts of the signal of the N-acetyl group among all the s ignals in Me betaGlcNAc were observed in H-1 NMR spectra of mixtures o f HOL-I and the sugar. Among the oligosaccharides tested, GlcNAcbeta1- ->4(GlcNAcbeta1-->2)Manalpha1-O(CH2)2 CH3 was the most potent inhibito r, and the inhibitory potency of the oligosaccharide was 2(4) times gr eater than those of GlcNAc and GalNAc. On the other hand, N-acetyllact osamine (Galbeta1-->4GlcNAc) and its analogs were the strongest inhibi tors toward HOL-II-induced hemagglutination. The agglutination was com pletely inert to Galbeta1-->3GlcNAc, Galbeta1-->6GlcNAc, Galbeta1-->3G alNAc, Galbeta1-4GalNAc, and Galbeta1-->6GalNAc. Furthermore, HOL-II e xhibited no binding ability to BSM, asialo-BSM, fetuin, asialofetuin, alpha1-acid glycoprotein, and human transferrin. These results indicat e that HOL-II strictly recognizes simple Galbeta1-->4GlcNAc unit.