Plant members of the α1→3/4-fucosyltransferase gene family encode an α1→4-fucosyltransferase, potentially involved in Lewisa biosynthesis, and two core α1→3-fucosyltransferases

Three putative alpha1 --> 3/4-fucosyltransferase (alpha1 --> 3/4-FucT) genes have been detected in the Arabidopsis thaliana genome. The products of two of these genes have been identified in vivo as core alpha1-3-FucTs involved 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 product is alpha1 --> 4-fucosylated at the N-acetylglucosamine residue. In vitro, the recombinant B. vulgaris alpha1 --> 4-FucT acts efficiently only on neutral type 1 chain-based glycan structures. In plants the enzyme is expected to be involved in Lewis(a) formation on N-linked glycans. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.