Identification of a cDNA encoding a plant Lewis-type α1,4-fucosyltransferase

Recently, it has been found that plants, including tomato (Lycopersicon esculentum), express the Lewis-a epitope, Galbeta1,3(Fucalpha1,4)GlcNAc, on some N-glycans. By searching the EST database, it was possible to identify a tomato cDNA encoding a protein, designated FucTC, of 413 amino acids with homology to plant and mammalian alpha1,3/4-fucosyltransferases. The cDNA was expressed in Pichia pastoris and the recombinant enzyme was found to transfer fucose from GDP-Fuc (K-m 16 muM) to lacto-N-tetraose (Galbeta1,3GlcNAcbeta1,3Galbeta1,4Glc; K-m 80 muM) as well as to beta1,3- and beta1,4-galactosylated N-glycans. It is concluded that FucTC is responsible for the biosynthesis of Lewis-a on N-glycans in tomato.