Catalyzes the two-step NADP-dependent conversion of GDP-4-dehydro-6-deoxy-D-mannose to GDP-fucose, involving an epimerase and a reductase reaction. Not involved in the synthesis of GDP-L-galactose from GDP-D-manose. GDP-beta-L-fucose + NADP(+) = GDP-4-dehydro-alpha-D-rhamnose + H(+) + NADPH Nucleotide-sugar biosynthesis; GDP-L-fucose biosynthesis via de novo pathway; GDP-L-fucose from GDP-alpha-D-mannose: step 2/2. Binds and stabilizes MUR1. Homodimer (By similarity). Highly expressed in roots and flowers, less abundant in leaves, stems and siliques. Belongs to the NAD(P)-dependent epimerase/dehydratase family. Fucose synthase subfamily. Truncated N-terminus.