Characterization of a core alpha 1 -> 3-fucosyltransferase from the snail Lymnaea stagnalis that is involved in the synthesis of complex-type N-glycans

We have identified a core alpha 1 --> 3-fucosyltransferase activity in the albumin and prostate glands of the snail Lymnaea stagnalis. Incubation of a lbumin gland extracts with GDP-[C-14]Fuc and asialo/agalacto-glycopeptides from human fibrinogen resulted in a labeled product in 50% yield. Analysis of the product by 400 MHz H-1-NMR spectroscopy showed the presence of a Fuc residue alpha 1 --> 3-linked to the Asn-linked GlcNAc. Therefore, the enzy me can be identified as a GDP-Fuc:GlcNAc (Asn-linked) alpha 1 --> 3-fucosyl transferase. The enzyme acts efficiently on asialo/agalacto-glycopeptides f rom both human fibrinogen and core alpha 1 --> 6-fucosylated human IgG, whe reas bisected asialo/agalacto-glycopeptide could not serve as an acceptor. We propose that the enzyme functions in the synthesis of core alpha 1 --> 3 -fucosylated complex-type glycans in L. stagnalis. Core alpha 1 --> 3-fucos ylation of the asparagine-linked GlcNAc of plant- and insect-derived glycop roteins is often associated with the allergenicity of such glycoproteins. S ince allergic reactions have been reported after consumption of snails, the demonstration of core alpha 1 --> 3-fucosylation in L. stagnalis may be cl inically relevant, (C) 1999 Federation of European Biochemical Societies.