MECHANISM OF THE OXIDATION OF HEMOGLOBIN BY COPPER (II) COMPLXES

Abstract

An outer sphere electron transfer mechanism by which human hemoglobin reduces the complexes of copper(II) and, in turn, is oxidized to methemoglobin has been characterized. We have found that the rate of oxidation of hemoglobin is a function of pH, temperature, concentration of copper(II), and the environment of the hemoglobin. Prior to oxidation, copper(II) complex binds to specific sites on the surface of the protein by losing one or more of its ligands, forming a ternary complex. This process is followed by electron transfer between the Cu(II) and Fe(H) with the Cu(II)-deoxyhemoglobin being the active intermediate. The dominant factors which govern the rate of oxidation of hemoglobin by coppcr(I I) complexes seem to be the stability constant of the Cu(II) complexes and the overall redox potential of the ternary complex.