Synthesis of alpha-Gal epitope derivatives with a galactosyltransferase-epimerase fusion enzyme.

Alpha-Gal epitopes are carbohydrate structures bearing an alpha-D-Galp-(1-->3)-beta-D-Galp terminus and are the main cause of antibody-mediated hyperacute rejection in xenotransplantation. Nine monosaccharides and ten disaccharides were evaluated as substrates for a fusion protein, which contains both alpha-(1-->3)-galactosyltransferase and uridine-5'-diphosphogalactose 4-epimerase. Four disaccharide and six trisaccharide alpha-Gal epitope derivatives were synthesized utilizing this novel fusion enzyme.