Phosphomannomutase 1 (PMM1) blongs to the eukaryotic PMM family. Phosphomannomutase 1 can catalyzes the conversion between D-mannose 6-phosphate and D-mannose 1-phosphate which is a substrate for GDP-mannose synthesis. GDP-mannose is used for synthesis of dolichol-phosphate-mannose which required for a number of critical mannosyl transfer reactions. PMM1 is highly expressed in liver, heart, brain, and pancreas, but lower expression in skeletal muscle. In addition, PMM1 may be responsible for the degradation of glucose-1,6 bisphosphate in ischemic brain.

GDP-L-Fucose Synthase is a NADP(H)-binding protein. It catalyzes the two-step epimerase and the reductase reactions in GDP-D-mannose metabolism, converting GDP-4-keto-6-D-dexoymannose to GDP-L-fucose. GDP-L-Fucose is the substrate of several fucosyltransferase, involving the expression of mamy glycoconjugates, including blood group ABH antigens and development adhesion antigens. Mutations in the TSTA3 gene may cause leukocyte adhesion deficiency type II.