Enhancement of the Acid and Alkaline Bohr Effects of Hemoglobin by Organic Phosphates
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The alkaline Bohr effect (release of protons as a result of the oxygenation of hemoglobin) has been shown to be enhanced in human hemoglobin in the presence of 2,3-diphosphoglycerate (1–4). A similar enhancement of the Bohr effect has been found in studies of certain fish hemoglobins (5). Both Bailey et al. (2) and De Bruin et al. (6) have reported differential titration experiments which show enhancement not only of the alkaline Bohr effect but also of the acid Bohr effect. That is, oxygenation of human hemoglobin at sufficiently low pH is associated with an additional uptake of protons in the presence of 2,3-diphosphoglycerate. The data of De Bruin et al. (6) but not those of Bailey et al. (2) suggested that this additional uptake was, in fact, equal to the additional release of protons which occurs in alkaline solution. These experiments are not sufficient by themselves to ascertain whether the oxygen affinity is raised or lowered in the presence of organic phosphates at low pH. We have therefore undertaken a study of the oxygen equilibrium to determine which of these two alternatives may prevail.
KeywordsOxygen Affinity Organic Phosphate Oxygen Equilibrium Protonated Species Human Hemoglobin
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