Differences in the interaction of 2,3-diphosphoglycerate with certain mammalian hemoglobins

The hemoglobins of man, horse, dog, rabbit, guinea pig, and rat all have relatively high (nonphysiologic) oxygen affinity when stripped of organic phosphates, and a strong reactivity with 2,3-diphosphoglycerate (2,3-DPG). Appropriately, their red cells contain high levels of 2,3-DPG. In contrast, the sheep, goat, cow, and cat have low oxygen affinity hemoglobins which interact weakly with 2,3-DPG, and low concentrations of red cell 2,3-DPG. These hemoglobins have structural differences at the NH(2)-terminus of the beta chain, a site where 2,3-DPG is thought to bind.