A plant fucosyltransferase with human Lewis blood-group specificity.

A fucosyltransferase from mung bean seedling was found to transfer L-fucose from GDP-fucose to the Type 1 disaccharide beta-D-Galp-(1----3)-beta-D-GlcpNAc-OR [R = (CH2)8COOMe]. The product, which was detected by an anti-Lea antibody in a novel ELISA assay, was isolated and shown to be the human Lea blood-group determinant beta-D-Galp-(1----3)-[alpha-L-Fucp-(1----4)]-beta-D-GlcpNAc-OR by 1H-n.m.r. spectroscopy. This enzyme activity is distinct from that of the human Lewis-fucosyl-transferase since alpha-L-Fucp-(1----2)-beta-D-Galp-(1----4)-beta-D-Glcp-OR is a very poor substrate, while the Type 2 disaccharide beta-D-Galp-(1----4)-beta-D-GlcpNAc-OR is not an acceptor. In common with the Lewis fucosyltransferase, the H-Type 1 trisaccharide alpha-L-Fucp-(1----2)-beta-D-Galp-(1----3)-beta-D-GlcpNAc-OR was an excellent substrate for the enzyme. This new enzyme activity was further characterized with respect to pH, nucleotide, Mn2+ dependence, and acceptor specificity against a panel of synthetic oligosaccharides.