From the Research
2,3-bisphosphoglycerate (2,3-BPG) is the glycolytic intermediate that decreases hemoglobin's affinity for oxygen. This molecule binds to the beta subunits of deoxyhemoglobin, stabilizing the T (tense) state and making it harder for oxygen to bind to hemoglobin. The physiological mechanism of 2,3-BPG is crucial for efficient oxygen delivery to tissues, as it promotes oxygen release in areas where it's needed most, particularly under conditions of hypoxia or increased metabolic demand 1.
Some key points about 2,3-BPG include:
- It is a major modulator of hemoglobin oxygen affinity and hence is vital in blood oxygen transport and delivery 2, 3.
- The feedback inhibition of hexokinase and phosphofructokinase by 2,3-BPG are equally as important as the product inhibition of 2,3-BPG synthase in controlling the normal in vivo steady-state concentration of 2,3-BPG 2.
- H+ and oxygen are effective regulators of 2,3-BPG concentration and that increases in 2,3-BPG concentrations are achieved with only small changes in glycolytic rate 2.
- The interaction between 2,3-BPG and hemoglobin represents an important adaptation that enhances oxygen delivery efficiency, particularly under conditions of hypoxia or increased metabolic demand 1, 4.
When oxygen levels are low, such as in high-altitude environments or during exercise, red blood cells increase their production of 2,3-BPG, which shifts the oxygen-hemoglobin dissociation curve to the right 1. This rightward shift means that at any given oxygen partial pressure, hemoglobin will release more oxygen to tissues. The role of 2,3-BPG in the intraerythrocytic adaptation to various types of hypoxaemia is described in detail in the literature 1.
In terms of clinical implications, the increased oxygen affinity of blood stored in acid-citrate-dextrose (ACD) solution has been shown to be due to the decrease in the concentration of 2,3-BPG which occurs during storage 1. Methods of maintaining the concentration of 2,3-BPG in stored blood are described, and the clinical implication of transfusion of elderly people, anaemic or pregnant patients with ACD stored blood to anaesthetically and surgically acceptable haemoglobin concentrations are discussed 1.
Overall, the evidence suggests that 2,3-BPG plays a critical role in regulating hemoglobin's affinity for oxygen, and its interaction with hemoglobin is essential for efficient oxygen delivery to tissues, particularly under conditions of hypoxia or increased metabolic demand 1, 5, 4, 2, 3.