Highly efficient chemoenzymatic synthesis of α-galactosyl epitopes with a recombinant α(1→3)-galactosyltransferase

alpha-Galactosyl epitopes are carbohydrate structures bearing a Gal alpha 1-3Gal beta terminus. The interaction of these epitopes on the surface of animal cells with anti-alpha-galactosyl antibodies in human serum is believed to be the main cause in antibody-mediated hyperacute rejection in xenotransplantation. This report describes an efficient chemoenzymatic approach based on the use of recombinant alpha(1 --> 3)-galactosyltransferase (alpha 1,3-GalT) for the synthesis of xenoactive alpha-galactosyl epitopes, which are highly desired in the research of xenotransplantation and immunotherapy. A truncated bovine alpha 1,3-GalT (80-368) was cloned into the pET15b vector-and Subsequently transformed into E. coli BL21 strain. This expression system efficiently produced the soluble recombinant enzyme on a large scale with highly specific activity. A variety of alpha(1 --> 3)galactosylated epitopes were synthesized using such a recombinant enzyme. In a unique fashion, alpha-galactosyl pentasaccharide was synthesized via a one-pot, two-step enzymatic synthesis with in situ cofactor regeneration.