EPR STUDIES ON THE EFFECTS OF COMPLEXATION OF HEME BY HEMOPEXIN UPON ITS REACTIONS WITH ORGANIC PEROXIDES

Hemopexin, a heme-binding serum glycoprotein, is thought to play an im portant role in the prevention of oxidative damage that may be catalys ed by free heme. Through the use of EPR techniques, the generation of free radicals from organic hydroperoxides by heme and heme-hemopexin c omplexes, and the concomitant formation of high oxidation-state iron s pecies has been studied; these species are implicated as causative age nts in processes such as cardiovascular disease and carcinogenesis. Fr om the rates of production of these species from both n-alkyl and bran ched hydroperoxides, it has been inferred that the dramatic reduction in the yield of oxidising species generated by heme upon its complexat ion with hemopexin arises from steric hindrance of the access of hydro peroxide to the bound heme.