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.