Interconversion of 3- and 2-phosphoglycerate with 2,3-bisphosphoglycerate as the primer of the reaction. Can also Catalyzes the reaction of EC 5.4.2.4 (synthase), but with a reduced activity. (2R)-2-phosphoglycerate = (2R)-3-phosphoglycerate Inhibited by inositol hexakisphosphate and benzene tri-, tetra- and hexacarboxylates. kcat is 490 sec(-1) for the mutase reaction, 0.0074 sec(-1) for the synthase reaction and 0.0087 sec(-1) for the phosphatase reaction with 3-phosphoglycerate as substrate. Carbohydrate degradation; glycolysis; pyruvate from D-glyceraldehyde 3-phosphate: step 3/5. Homotetramer: dimer of dimers. Present with 172000 molecules/cell in log phase SD medium. Belongs to the phosphoglycerate mutase family. BPG-dependent PGAM subfamily.