GDP-L-FucN-acetyl-β-D-glucosaminide α1-6fucosyltransferase (FUT8) catalyzes the transfer of fucose from GDP-Fuc to N-linked-type complex glycoproteins, as shown in Fig. 1. The enzymatic products, α1,6-fucosylated (core fucosylated) N-glycans, are commonly observed in many glycoproteins, and are especially abundant in brain tissue. It is well known that the sugar chains in α-fetoprotein (AFP), a well-known tumor marker of hepatocellular carcinoma, are microheterogenous in nature to sugar chains. The oligosaccharide structures of transferrin as well as AFP, synthesized by hepatocellular carcinoma cells, are highly fucosylated (Champion et al. 1989). In contrast, FUT8 is released from platelets during blood clotting (Koscielak et al. 1987), suggesting that this enzyme might play a role in blood coagulation. An increase in fucosylated carbohydrates in pathological conditions has also been reported in other types of cancer cells (Tatsumura 1977). Open image in new window Fig. 1 Reaction pathway of FUT8. GlcNAc indicates N-acetylglucosamine, Man indicates mannose, Fuc indicates fucose, GDP-Fuc indicates guanosinediphosphofucopyranoside, and Asn indicates asparagine