GDP-fucose protein O-fucosyltransferase 2 (POFUT2) is an enzyme responsible for adding fucose sugars in O linkage to serine or threonine residues in Thrombospondin repeats.[5] The protein is an inverting glycosyltransferase, which means that the enzyme uses GDP-β-L-fucose as a donor substrate and transfers the fucose in O linkage to the protein producing fucose-α-O-serine/threonine.