One-pot three-enzyme synthesis of Lewis x trisaccharide Galβ1–4(Fucα1–3)GlcNAcβProN3 or sialyl Lewis x tetrasaccharide Neu5Acα2–3Galβ1–4(Fucα1–3)GlcNAcβProN3 from L-fucose, ATP, GTP, type II disaccharide Galβ1–4GlcNAcβProN3 or trisaccharide Neu5Acα2–3Galβ1–4GlcNAcβProN3. FKP, a recombinant bifunctional L-fucokinase/GDP-fucose pyrophosphorylase (FKP) from Bacteroides fragilis 9343; PmPpA, Pasteurella multocida inorganic pyrophosphatase. Hp1–3FTΔ66, a recombinant Helicobacter pylori α1–3-fucosyltransferase with a C-terminal 66 amino-acid-residue truncation.