TLC analysis of enzymatic synthesis of GDP–fucose. The developing solvent used was n-butanol:acetic acid:water = 2:1:1 (v/v/v). The plate was stained with p-anisaldehyde sugar stain. Lane: 1, l-fucose; 2, ATP; 3, reaction mixture without l-fucose pyrophosphorylase (FKP); 4, reaction mixture without GTP; and 5, alkaline phosphatase-treated reaction mixture of GDP-fucose synthesis.