A Redox‐Controlled Substrate Engineering Strategy for Site‐Specific Enzymatic Fucosylation

Fucosylation is one of the most common modifications of oligo-N-acetyllactosamine (oligo-LacNAc) glycans. However, none of known fucosyltransferases (FucTs) could install the alpha 1,3-linked fucose to the oligo-LacNAc substrates in a site-specific manner. Here, we report a facile and general redox-controlled substrate engineering strategy for the site-specific alpha 1,3-fucosylation of complex glycans containing multiple LacNAc units. This strategy takes advantage of an operationally simple oxidation enzyme module by using galactose oxidase (GOase) to convert the LacNAc unit into oxidized C6 '-aldehyde LacNAc sequence, which is not a good substrate for recombinant alpha 1,3-FucT from Helicobacter pylori strain 26695 (Hp alpha 1,3FucT), enabling the site-specific alpha 1,3-fucosylation at intact LacNAc sites. The general applicability and robustness of this strategy were demonstrated by the synthesis of a variety of structurally well-defined fucosides of linear and branched O- and N-linked glycans.