Most members of this family are phosphoglycerate mutase (EC: 5.4.2.1). This enzyme interconverts 2-phosphoglycerate and 3-phosphoglycerate. 2-phospho-D-glycerate + 2,3-diphosphoglycerate = 3-phospho-D-glycerate + 2,3-diphosphoglycerate. The enzyme is transiently phosphorylated on an active site histidine by 2,3-diphosphoglyerate, which is both substrate and product. Some members of this family have are phosphoglycerate mutase as a minor activity and act primarily as a bisphoglycerate mutase, interconverting 2,3-diphosphoglycerate and 1,3-diphosphoglycerate (EC: 5.4.2.4).