Peroxidase activity of hemoglobin and its subunits: Effects thereupon of haptoglobin

Abstract

Studies of the peroxidase activity of human hemoglobin A and its separated α and β subunits have shown that native hemoglobin possesses greater peroxidase activity than isolated subunits containing an equivalent amount of heme. Upon recombination of unlike subunits, peroxidase activity approaches that of an equivalent quantity of native hemoglobin. Similar results were obtained when hemoglobin H ( β 4 A) replaced β subunits prepared from hemoglobin A. It is concluded that the peroxidase activity of the heme moiety, like its binding behavior with gaseous ligands, is affected by interactions between unlike polypeptide chains. Experiments are presented which suggest that haptoglobin enhances the peroxidase activity of the heme moiety through conformational effects on the globin moiety.