Effect of carbon dioxide on human hemoglobin. Kinetic basis for the reduced oxygen affinity.

The kinetic basis for the reduction in the oxygen affinity of hemoglobin due to carbon dioxide at constant pH, is studied by measuring the deoxygenation rates of oxyhemoglobin with dithionite, as well as the rate of binding of carbon monoxide to deoxyhemoglobin. These studies were performed in buffer containing 0.05 M potassium phosphate, as well as various mixtures of potassium chloride and potassium bicarbonate all at a constant pH of 7.5 and 23’. The results indicate that the reduction in the ligand affinity of hemoglobin by carbon dioxide is the result of a reduced rate of ligand binding with no significant change in the rate of release. It is pointed out that this result is in contrast to salts which reduce the ligand affinity of hemoglobin by increasing the rate of ligand dissociation as well as reducing the rate of ligand binding.