In the 'de novo' GDP-L-fucose biosynthetic pathway, GDP-L-fucose is produced from GDP-D-mannose via a 2-step process in the cytosol and then imported in the Golgi apparatus where fucosyltransferases use it as a fucose donor for the N- and O-fucosylation of proteins and lipids.This is the only pathway for GDP-L-fucose biosynthesis in D. melanogaster as the enzymes involved in the salvage pathway - which uses L-fucose as a substrate - are not present in the Dmel genome. (Adapted from FBrf0144936.)