ENZYMATIC-SYNTHESIS OF A 6'-SULFATED SIALYL-LEWIS(X) WHICH IS AN INHIBITOR OF L-SELECTIN BINDING TO PERIPHERAL ADDRESSIN

A sulphated form of sialyl-Lewis(x), NeuAc alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc6OSO(3) beta 1-3Gal, was synthesized enzymatically from a precursor disaccharide, GlcNAc6OSO(3) beta 1-3Gal, using sequential steps involving beta 1,4-galactosyltransferase, alpha 2,3-trans-sialidase and recombinant alpha 1,3-fucosyltransferase, respectively, Successful enzymatic fucosylation at the 3 position of the GlcNAc6OSO(3) residue demonstrated that fucosyltransferases are capable of generating, in situ, sulphated sialyl Lewis(x) structures containing sulphate at the 6 position of GlcNAc. The sulphated sialyl-Lewis(x) pentasaccharide produced by this procedure inhibited binding of a soluble form of L-selectin to (SO4)-S-35-labelled peripheral addressin with an IC50 of 0.8 mM, whereas sialyl-Lewis(x) tetrasaccharide was a weaker inhibitor, displaying an IC50 of 3.2 mM, Hemmerich and Rosen (Biochemistry, 33, 4820-4829, 1994) recently reported the presence of Gal beta 1-4GlcNAcO6SO(3) structures on murine peripheral addressin Sgp50, in addition to sialyl Lewis(x) structures sulphated at the 6-O-galactose position, Based on our data, we suggest that sialyl Lewis(x) sulphated at the 6-O-GlcNAc position may also exist on receptors and function as a ligand for L-selectin.