Organic phosphates and ligand binding in hemoglobin.
Abstract Although several organic phosphates appear to react rapidly with hemoglobin, and to be nearly at equilibrium with the various intermediates during oxygen binding, pyridoxal phosphate reacts quite slowly, allowing study of the properties of intermediates bound both to organic phosphate and to oxygen. The affinity for oxygen and the n value are much decreased as compared with stripped hemoglobin. It has been calculated that about a third to a half of the heme-heme interaction energy is associated with binding of organic phosphates or other anions, in a linked reaction occurring only with tetrameric hemoglobin, which must therefore be considered as the smallest unit permitting a meaningful. description of hemoglobin-ligand interactions.