Kinetics of peroxidase activity, absorption spectra and oxygen affinity of human hemoglobin-haptoglobin 1-1 complexes

Some functional properties of the intermediate and saturated forms of human hemoglobin-haptoglobin 1-1 complex were studied to clucidate the interaction between these two proteins. No significant difference was demonstrated in the kinetics of peroxidase activity and the Soret band spectra of these two complexes under the various conditions studied. Furthermore, both of the complexes have a very high affinity for oxygen, with values of n approximately I, indicating the absence of heme-heme interaction. These results seem to indicate that the similar changes in the configurations of hemoglobin moieties are induced by the binding with haptoglobin in these complexes. Therefore, the same type of molecular interaction between hemoglobin αβ-dimers and haptoglobin will be involved in both complexes.