Highly Efficient Chemoenzymatic Synthesis of α-Galactosyl Epitopes with a Recombinant α(1→3)-Galactosyltransferase

Abstract

α-Galactosyl epitopes are carbohydrate structures bearing a Galα1-3Galβ terminus. The interaction of these epitopes on the surface of animal cells with anti-α-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 α(1→3)-galactosyltransferase (α1,3-GalT) for the synthesis of xenoactive α-galactosyl epitopes, which are highly desired in the research of xenotransplantation and immunotherapy. A truncated bovine α1,3-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 α(1→3)-galactosylated epitopes were synthesized using such a recombinant enzyme. In a unique fashion, α-galactosyl pentasaccharide was synthesized via a one-pot, two-step enzymatic synthesis with in situ cofactor regeneration.