2,3-Bisphosphoglycerate (2,3-BPG)

The molecule 2,3-disphosphoglycerate (2,3-DPG ) binds to hemoglobin and lowers its affinity for oxygen, thus promoting oxygen release. In individuals who have become acclimatized to living at high altitudes, the level of 2,3-DPG in the blood increases, allowing the delivery of more oxygen to tissues under low oxygen tension.

2,3-Bisphosphoglycerate  is a three carbon isomer of the glycolytic intermediate 1,3-bisphosphoglycerate. 2,3-BPG is present in human red blood cells (RBC; erythrocyte) at approximately 5 mmol/L. It binds with greater affinity to deoxygenated hemoglobin (e.g. when the red cell is near respiring tissue) than it does to oxygenated hemoglobin (e.g. in the lungs). In bonding to partially deoxygenated hemoglobin it allosterically upregulates the release of the remaining oxygen molecules bound to the hemoglobin, thus enhancing the ability of RBCs to release oxygen near tissues that need it most.