FUT5 (alpha-1, 3-fucosyltransferase 5; also Fuc-TV) is a 43kD member of the glycosyltransferase 10 family. It is responsible for the terminal step in the synthesis of Le, sialyl-Le, and Le antigens. This is accomplished by the transfer of fucose to preexisting LacNAc or sialyl-LacNAc structures. Human FUT5 is 374 amino acids (aa) in length. It is a type II transmembrane Golgi glycoprotein with a C-terminal lumenal domain (aa35-374). The catalytic domain spans aa77-374, while the acceptor-binding motif includes aa120-126. FUT5 is the product of a single exon gene. Thus, there are no splice variants. FUT5 only occurs in primates; there is no rodent ortholog.