2,3-Bisphosphoglyceric Acid

2,3-Bisphosphoglyceric acid (2,3-Bisphosphoglycerate or 2,3-BPG, also known as 2,3-diphosphoglycerate or 2,3-DPG) is a three-carbon isomer of the glycolytic intermediate 1,3-bisphosphoglyceric acid (1,3-BPG). 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) due to spatial changes: 2,3-BPG (whose size is estimated at about 9 angstroms) fits in the deoxygenated hemoglobin configuration (11 angstroms), but not as well in the oxygenated (5 angstroms). It interacts with deoxygenated hemoglobin beta subunits by decreasing their affinity for oxygen, so it allosterically promotes 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. 2,3-BPG is thus an allosteric effector.

Its function was discovered in 1967 by Reinhold Benesch and Ruth Benesch.