Enzymatic synthesis of α-l-fucosyl-N-acetyllactosamines and 3′-O-α-l-fucosyllactose utilizing α-l-fucosidases

An α-l-fucosidase from porcine liver produced α-l-Fuc-(1→2)-β-d-Gal-(1→4)-d-GlcNAc (2′-O-α-l-fucosyl-N-acetyllactosamine, 1) together with its isomers α-l-Fuc-(1→3)-β-d-Gal-(1→4)-d-GlcNAc (2) and α-l-Fuc-(1→6)-β-d-Gal-(1→4)-d-GlcNAc (3) through a transglycosylation reaction from p-nitrophenyl α-l-fucopyranoside and β-d-Gal-(1→4)-d-GlcNAc. The enzyme formed the trisaccharides 1–3 in 13% overall yield based on the donor, and in the ratio of 40:37:23. In contrast, transglycosylation by Alcaligenes sp. α-l-fucosidase led to the regioselective synthesis of trisaccharides containing a (1→3)-linked α-l-fucosyl residue. When β-d-Gal-(1→4)-d-GlcNAc and lactose were acceptors, the enzyme formed regioselectively compound 2 and α-l-Fuc-(1→3)-β-d-Gal-(1→4)-d-Glc (3′-O-α-l-fucosyllactose, 4), respectively, in 54 and 34% yields, based on the donor.