Guanylyltransferase enzymes transfer one molecule of GTP to another molecule and also function in the transfer of guanosine nucleotides to sugar molecules. The carbohydrate moieties that are generated are covalently attached to cell surfaces and are necessary to ensure a surface contour that satisfies a variety of physiological roles. L-fucose is an important sugar in complex carbohydrates that is frequently found on plant and mammalian N-linked glycans. FPGT (Fucose-1-phosphate guanylyltransferase), also known as GFPP (GDP-L-fucose pyrophosphorylase), is a 594 amino acid cytoplasmic protein that catalyzes the formation of GDP-L-fucose from L-fucose-1-phosphate and GTP. FPGT functions to reutilize the L-fucose that is produced uopn glycoprotein and glycolipid turnover.