Function, Metabolism, and Regulation of Organic Phosphates in Erythrocytes

Function, Metabolism, and Regulation of Organic Phosphates in Erythrocytes 

Effect of 2,3-bisphosphoglycerate (2,3-DPG) on the oxygen saturation curve of hemoglobin. Note that 2,3-DPG decreases the affinity of hemoglobin for oxygen. 

In other mammals, including horse, dog, pig, and guinea pig, fetal hemoglobin is not structurally different from adult hemoglobin, and transplacental diffusion is facilitated by a reduced concentration of 2,3-DPG in fetal erythrocytes. In ruminants, hemoglobin does not bind 

3-DPG because the jS chains are too far apart. However, fetal hemoglobin in ruminants has a higher affinity for oxygen than does adult hemoglobin because of other structural differences. These three different solutions to the problem of the need for transfer of oxygen to the fetus are an example of convergent evolution. 

The binding of 2,3-DPG to deoxyhemoglobin decreases the amount of free 2,3-DPG available for participation in other reactions and causes increased 2,3-DPG synthesis at the expense of 1,3-bisphospho-glycerate. A decrease in oxygen saturation of hemoglobin may act in the same way. 

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