HIGHLY EFFICIENT CHEMOENZYMATIC SYNTHESIS OF ALPHA-GALACTOSYL EPITOPES WITH A RECOMBINANT ALPHA(1-]3)-GALACTOSYLTRANSFERASE

alpha-Galactosyl epitopes are carbohydrate structures bearing a Gal al pha 1-3Gal beta terminus. The interaction of these epitopes on the sur face of animal cells with anti-alpha-galactosyl antibodies in human se rum is believed to be the main cause in antibody-mediated hyperacute r ejection in xenotransplantation. This report describes an efficient ch emoenzymatic approach based on the use of recombinant alpha(1 --> 3)-g alactosyltransferase (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-G alT (80-368) was cloned into the pET15b vector-and Subsequently transf ormed into E. coli BL21 strain. This expression system efficiently pro duced the soluble recombinant enzyme on a large scale with highly spec ific activity. A variety of alpha(1 --> 3)galactosylated epitopes were synthesized using such a recombinant enzyme. In a unique fashion, alp ha-galactosyl pentasaccharide was synthesized via a one-pot, two-step enzymatic synthesis with in situ cofactor regeneration.