?1,3-Fucosylation of branched blood group I-type oligo-(N-acetyllactosamino)glycans by human milk transferases is restricted to distalN-acetyllactosamine units: The resulting isomers are separated by WGA-agarose chromatography

Abstract

A partially purified preparation of alpha 1,3-fucosyltransferase(s) from human milk was used to [14C]fucosylate oligosaccharides containing Gal beta 1-4GlcNAc units. Substitution of N-acetyllactosamine at position 3' with a beta-linked N-acetyl-glucosamine enhanced the reactivity of the acceptor, whereas similar substitution at position 6' was inhibitory. Thus, the trisaccharide GlcNAc beta 1-6Gal beta 1-4GlcNAc (5), the branched tetrasaccharide GlcNAc beta 1-3(GlcNAc beta 1-6)Gal beta 1-4GlcNAc (11) and the triply branched decasaccharide GlcNAc beta 1-3(GlcNAc beta 1-6)Gal beta 1-4GlcNAc beta 1-3[GlcNAc beta 1-3(GlcNAc beta 1-6)Gal beta 1-4GlcNAc beta 1-6]Gal beta 1-4GlcNAc (26) gave remarkably poor yields of alpha 1,3-fucosylated products in comparison to GlcNAc beta 1-3Gal beta 1-4GlcNAc (3). beta 1,4-Galactosyl derivatives of 5 and 11, however, gave good yields of alpha 1,3-fucosylated products, but the fucosylation was restricted to the distal N-acetyllactosamine units of Gal beta 1-4GlcNAc beta 1-6Gal beta 1-4GlcNAc (16), Gal beta 1-4GlcNAc beta 1-3(Gal beta 1-4GlcNAc beta 1-6)Gal beta 1-4GlcNAc (18) and also in Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-3(Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-6)Gal beta 1-4GlcNAc (22). Immobilized wheat germ agglutinin (WGA), possessing high affinity for 16 [1], revealed no affinity for the fucosylated derivative Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-6Gal beta 1-4GlcNAc (17). The isomeric heptasaccharides Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3(Gal beta 1-4GlcNAc beta 1-6)Gal beta 1-4GlcNAc (19) and Gal beta 1-4GlcNAc beta 1-3[Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-6]Gal beta 1-4GlcNAc (20) were readily separated from each other on WGA agarose, and so were the isomeric nonasaccharides Gal alpha 1-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3(Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-6)Gal beta 1-4GlcNAc (23) and Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-3[Gal alpha 1-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-6]Gal beta 1-4GlcNAc (24).