Fucosylation of complex glycosphingolipids by recombinant fucosyltransferase-VII.

Fucosyltransferase VII (FucT-VII) is one of five known alpha 1-->3fucosyltransferases capable of transferring fucose to the C-3 position of N-acetylglucosamine residues found in lactosamine based glycans. Previous studies have indicated that FucT-VII has a very restricted specificity, capable of fucosylating only terminally alpha 2-->3sialylated carbohydrate substrates, resulting in the synthesis of the sialyl Lewis x (sLe(x)) epitope. Although FucT-VII is expressed in cells of myeloid origin, the monosialylganglioside fraction of HL60 cells contains only internally and/or multiply fucosylated polylactosamine structures; no monofucosylated sLe(x) derivatives are detected. We now report that the structure of the final product formed by the action of FucT-VII on sialynorhexaosylceramide (a glycosphingolipid substrate having multiple fucosylation sites) is extended monofucosyl sLe(x) and fucosylation is restricted to the terminal GlcNAc-V. This indicates that the biosynthesis of all fucosylated monosialylated gangliosides found in HL60 cells (including the E-selectin binding fractions) involves at least one additional alpha 1-->3fucosyltransferase.