Abstract
Abstract 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.
Highlights
The transferase showed a partial requirement for Mg++ and for Triton X-100
L-Fucose is kuown to occur in human blood group substances and human milk oligosaccharides (l-4) in the following linkages: (a) (a, 1 + 2) to galactose, the blood group H antigenic determinant, (b) (a, 1 + 4) to N-acetylglucosamine, the Lewis blood group antigenic determinant, and (c) ((Y, 1 + 3) to either glucose or N-acetylglucosamine
Fucosyl-(ar, 1 ---f 2)-galactosyl occurs in porcine submaxillary mucin [5]
Summary
Materials-Porcine liver was obtained fresh from Canada. Toronto, and kept on ice until used. L-Fucose-l-14C, 48.6 mCi per mmole, was purchased from Calbiochem and was diluted with nonradioactive L-fucose (Sigma) to give a specific activity of 4.35 mCi per mmole.
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