Plant members of the alpha 1 -> 3/4-fucosyltransferase gene family encode an alpha 1 -> 4-fucosyltransferase, potentially involved in Lewis(a) biosynthesis, and two core alpha 1 -> 3-fucosyltransferases

Three putative alpha1 --> 3/4-fucosyltransferase (alpha1 --> 3/4-FucT) gene s have been detected in the Arabidopsis thaliana genome. The products of tw o of these genes have been identified in vivo as core alpha1-3-FucTs involv ed in N-glycosylation. An orthologue of the third gene was isolated from a Beta vulgaris cDNA library. The encoded enzyme efficiently fucosylates Gal beta1 --> 3GlcNAc beta1 --> 3Gal beta1 --> 4Glc. Analysis of the product by 400 MHz H-1-nuclear magnetic resonance spectroscopy, showed that the produ ct is alpha1 --> 4-fucosylated at the N-acetylglucosamine residue. In vitro , the recombinant B. vulgaris alpha1 --> 4-FucT acts efficiently only on ne utral type 1 chain-based glycan structures. In plants the enzyme is expecte d to be involved in Lewis(a) formation on N-linked glycans. (C) 2001 Publis hed by Elsevier Science B.V. on behalf of the Federation of European Bioche mical Societies.