Enzymatic synthesis of a sialyl Lewis X dimer from egg yolk as an inhibitor of E-selectin

A dimeric sialyl Lewis X (SLe(x)) glycopeptide was synthesized enzymatically in three steps from an N-linked oligosaccharide prepared from egg yolk. Treatment of delipidated hen egg yolk with the protease Orientase and neuraminidase gave a dimeric N-acetyllactosamine-containing oligosaccharide linked to asparagine. Addition of sialic acid and fucose catalyzed by alpha-2,3-sialyltransferase and alpha-1,3-fucosyltransferase provided the dimeric SLe(x), which was shown to be as active as monomeric SLe(x) as an inhibitor of E-selectin with IC50 0.75 mM. The synthetic dimeric SLe(x) of the mucin type (i.e. SLe(x) linked to the 3- and 6-OH groups of Gal) is, however, about five times as active as the monomer. It is suggested that dimeric SLe(x) glycopeptides of the mucin type would be effective ligands for E-selectin.