Pork Liver Guanosine Diphosphate-l-Fucose Glycoprotein Fucosyltransferases

Two fucosyltransferases have been found in pork liver which transfer l-fucose from GDP-l-fucose into various derivatives of human plasma α1-acid glycoprotein. One of these enzymes incorporates l-fucose into the terminal positions of α1-acid glycoprotein prosthetic groups and into the disaccharide, galactosyl-(β,1 → 4)-N-acetylglucosamine. This enzyme does not transfer fucose to lactose, galactosyl(β,1 → 3)-N-acetylglucosamine, galactosyl-(β,1 → 6)-N-acetylglucosamine, and the α- and β-methyl-d-galactopyranosides. The substrate specificity indicates that the fucosyltransferase is responsible for the incorporation of l-fucose into plasma glycoproteins in vivo. The enzyme is membrane-bound and requires Triton X-100 and divalent cation for optimum activity. The other pork liver fucosyltransferase incorporates l-fucose into a position on the oligosaccharide prosthetic group of α1-acid glycoprotein at which l-fucose does not occur in the native glycoprotein; the function of this enzyme in pork liver is not known.