Bisphosphoglycerate mutase

Bisphosphoglycerate mutase (BPGM) catalyzes the conversion of 1,3-bisphosphoglycerate (1,3-BPG) to 2,3-bisphosphoglycerate (2,3-BPG). This enzyme should not be confused with Phosphoglycerate mutase (PGM) which plays a major role in glycolysis.

While 1,3-BPG is an important intermediate in Glycolysis, 2,3-BPG is not. 2,3-BPG does have an important role in erythrocytes, acting as an allosteric inhibitor of hemoglobin. The binding of 2,3-BPG decreases hemoglobin's affinity for oxygen and facilitates the transfer of O2 to tissues. BPGM plays an important role in erythrocytes, diverting up to 20% of the total glycolytic flux in order to maintain concentrations of 2,3-BPG that are roughly equal to concentrations of hemoglobin.

Excess amounts of 2,3-BPG can re-enter the glycolytic pathway through a phosphatase catalyzed conversion to glycerate 3-phosphate (G3P). This two-step process parallels Step 7 of main glycolytic pathway in which 1,3-BPG is converted directly to G3P with the phosphorylation of ADP to form ATP. The two-step BPGM/phosphatase pathway doesn't generate ATP and is therefore an inefficient way to arrive at G3P.