Bisphosphoglycerate mutase (BPGM) is an enzyme unique to erythrocytes and placental cells. This protein plays a major role in regulating hemoglobin oxygen affinity as a consequence of controlling 2,3-BPG concentration. It is responsible for the catalytic synthesis of 2,3-Bisphosphoglycerate (2,3-BPG) from 1,3-BPG. BPGM also has a mutase and a phosphatase function, but these are much less active.