Production of (alpha-Galactosyl Epitopes via Combined Use of Two Recombinant Whole Cells Harboring UDP-Galactose 4-Epimerase and alpha-l,3-Galactosyltransferase

alpha-Galactosyl epitopes (or (alpha-Gal, oligosaccharides with a terminal Galal,3Gal sequence) are a class of biologically important oligosaccharides in great demand in bulk quantities for basic and clinical studies on preventing hyperacute rejection in pig-to-primate organ xenotransplantaion. A truncated bovine alpha-l,3-galactosyltransferase, the key enzyme responsible for the biosynthesis of the terminal structure of alpha-Gal, was cloned and overexpressed previously. The acceptor specificity was further studied in the present paper, and lactose and galactose derivatives were found to be good acceptors. To develop a more proficient reaction process, we report herein an example of an efficient enzymatic synthesis of (alpha-Gal oligosaccharides catalyzed by the combination of two recombinant Escherichia coli whole cells harboring the genes of a UDP-galactose 4-epimerase and the o(-l,3-galactosyltransferase, respectively. Using lactosyl azide (LaeN3) as the acceptor for the glycosyltransferase, the combined use of the two recombinant cells efficiently produced a-Gal epitope Gala1,3LacN3 in 60-68% yield.