Binding of 2,3-Diphosphoglycerate and Adenosine Triphosphate to Human Haemoglobin A

The binding of 2,3-diphosphoglycerate and adenosine triphosphate to human haemoglobin was studied in solutions of a high haemoglobin concentration (3 mM) and varying amounts of 2,3-diphosphoglycerate, ATP, inorganic phosphate, magnesium and hydrogen ions. Both phospho compounds were found to be bound by both deoxygenated and oxygenated haemoglobin; the affinity of the former was at physiological conditions about twice that of the latter. At least two binding sites were found for 2,3-diphosphoglycerate; these sites show strong cooperation. Binding of both phospho compounds decreased at higher hydrogen ion concentration. Inorganic phosphate up to 10 mM had no effect on either compound. 2,3-Diphosphoglycerate decreased the binding of ATP to deoxygenated haemoglobin.