Enzymatic synthesis of two lacto-N-neohexaose-related Lewis x heptasaccharides and their separation by chromatography on immobilized wheat germ agglutinin.

Radiolabelled lacto-N-neohexaose was fucosylated with partially purified alpha (1,3)fucosyltransferase(s) from human milk. Structural analysis of the monofucosylated products obtained at an early stage of the reaction revealed that both distal branches of the acceptor had reacted equally well, generating Lewis x determinants, while the reducing end glucose had not reacted. The two isomeric Lewis x glycans were readily separated from each other by chromatography on immobilized wheat germ agglutinin (WGA), because alpha (1,3)fucosylation of the (1 --> 6)-linked branch of lacto-N-neohexaose was associated with a dramatic loss of WGA affinity. The fucosylation mixture of lacto-N-neohexaose also contained a difucosylderivative that carried Lewis x determinants at both distal branches. Attempted refucosylation of this octasaccharide failed to transfer fucose to the glucose unit.