Two 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 Halichondria okadai by affinity chromatography on a bovine submaxillary mucin (BSM)-Toyopearl and an acid-treated Sepharose 4B columns, respectively. In hemagglutination inhibition assays, GlcNAc, GalNAc, and their methyl glycosides were the most potent inhibitors among the monosaccharides tested against the HOL-I-mediated hemagglutination, suggesting that HOL-I can especially recognize the N-acetyl groups of the sugars. This N-acetyl specificity was supported by 1H NMR analyses; the highest field-shifts of the signal of the N-acetyl group among all the signals in Me beta GlcNAc were observed in 1H NMR spectra of mixtures of HOL-I and the sugar. Among the oligosaccharides tested, GlcNAc beta 1-->4(GlcNAc beta 1-->2)Man alpha 1-O(CH2)2 CH3 was the most potent inhibitor, and the inhibitory potency of the oligosaccharide was 2(4) times greater than those of GlcNAc and GalNAc. On the other hand, N-acetyllactosamine (Gal beta 1-->4GlcNAc) and its analogs were the strongest inhibitors toward HOL-II-induced hemagglutination. The agglutination was completely inert to Gal beta 1-->3GlcNAc, Gal beta 1-->6GlcNAc, Gal beta 1-->3GalNAc, Gal beta 1-->4GalNAc, and Gal beta 1-->6GalNAc. Furthermore, HOL-II exhibited no binding ability to BSM, asialo-BSM, fetuin, asialofetuin, alpha 1-acid glycoprotein, and human transferrin. These results indicate that HOL-II strictly recognizes simple Gal beta 1-->4GlcNAc unit.