Enzymatic properties of the beta-galactoside alpha 1 leads to 2 fucosyltransferase from porcine submaxillary gland.

Abstract

The acceptor substrate specificity and kinetic properties of the purified porcine submaxillary beta-galactoside alpha 1 leads to 2 fucosyltransferase have been examined. The transferase forms the Fuc alpha 1 leads to 2Gal linkage with oligosaccharides, glycoproteins, and glycolipids which contain nonreducing terminal galactose residues and shows no absolute specificity for a particular penultimate residue or for the linkage between the galactose and the penultimate residue. The fucosyltransferase is active in the absence of divalent metal ions, but it is stimulated upon addition of Mn2+, Mg2+, Ca2+, or Co2+. Kinetic analysis indicates an increase in the Km for both donor and acceptor substrates and in the Vmax in the presence of Mn2+. Initial rate studies and inhibition patterns suggest that the transferase has either a rapid equilibrium random kinetic mechanism or a steady state ordered mechanism with GDP-fucose binding first. Human "Bombay" erythrocytes which lack cell surface Fuc alpha 1 leads to 2Gal structures are fucosylated by the transferase, but expression of H blood group activity is dependent on treatment of the cells with neuraminidase. After neuraminidase digestion, the fucosylated cells are serologically identical to native O-type cells. Analysis of the fucosylated material in the erythrocyte membrane on sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggests that fucose is incorporated primarily into glycoprotein acceptors.