GDP-mannose 4,6-dehydratase catalyzes the conversion of GDP-mannose to GDP-4-keto-6-deoxymannose, the first step in the synthesis of GDP-fucose from GDP-mannose, using NADP+ as a cofactor. The second and third steps of the pathway are catalyzed by a single enzyme, GDP-keto-6-deoxymannose 3,5-epimerase, 4-reductase, designated FX in humans (MIM 137020). GMDS (GDP-Mannose 4,6-Dehydratase) is a Protein Coding gene. Diseases associated with GMDS include Congenital Disorder Of Glycosylation, Type Iic and Partial Fetal Alcohol Syndrome. Among its related pathways are Amino sugar and nucleotide sugar metabolism and Transport to the Golgi and subsequent modification.