Interconversion of 3- and 2-phosphoglycerate with 2,3-bisphosphoglycerate as the primer of the reaction. Can also catalyze the reaction of EC 5.4.2.4 (synthase), but with a reduced activity. (2R)-2-phosphoglycerate = (2R)-3-phosphoglycerate (2R)-3-phospho-glyceroyl phosphate = (2R)-2,3-bisphosphoglycerate + H(+) Homodimer. Interacts with ENO1. Expressed in the heart and muscle. Not found in the liver and brain. The disease is caused by variants affecting the gene represented in this entry. Belongs to the phosphoglycerate mutase family. BPG-dependent PGAM subfamily.