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.