Introduction of H-antigens into oligosaccharides and sugar chains of glycoproteins using highly efficient 1,2-α-l-fucosynthase.

Fuc alpha 1-2 Gal linkages, or H-antigens, constitute histo-blood group antigens and are involved in various physiological processes. In addition, recent studies have shown that the H-antigen-containing glycans play an important role, not only in establishing harmonious relationship between gut microbes and the host, but also in preventing gut dysbiosis-related diseases. Therefore, development of an efficient method for introducing Fuc residue at Gal residue at the nonreducing end of glycans via alpha-(1 -> 2) linkage is desired for research as well as medicinal purposes. In this study, we succeeded in derivatizing inverting 1,2-alpha-L-fucosidase (AfcA) into a highly efficient 1,2-alpha-L-fucosynthase. The synthase specifically synthesized H type 1-, type 2-, type 3- and type 4-chaincontaining oligosaccharides with yields of 57-75% based on acceptor depletion. The synthase was also able to specifically introduce Fuc residues into Lewis a/x antigens to produce Lewis b/y antigens, with yields of 43% and 62%, respectively. In addition, the enzyme efficiently introduced Hantigens into sugar chains of porcine gastric mucins, as revealed by lectin blotting and mass spectroscopy analysis of the sugars. Detailed acceptor specificity analysis using various monosaccharides and oligosaccharides unraveled unique substrate recognition feature of this synthase at the subsite (+1), which can be explained by our previous X-ray crystallographic study of AfcA. These results show that the synthase developed in this study could serve as an alternative to other H-antigen synthesis methods involving alpha-1,2-fucosyltransferases and retaining alpha-fucosidase.