Inhibition of heme-promoted enzymatic lipid peroxidation by desferrioxamine and EDTA

Oxyhemoglobin, methemoglobin and hematin were found to catalyze xanthine-oxidase-induced peroxidation of phospholipid liposomes, while oxy- and metmyoglobin were inactive in this respect. The peroxidation was inhibited by desferrioxamine and by EDTA. Peroxidation catalyzed by 0.4 μM oxyhemoglobin was decreased by 50% by approximately 2 μM desferrioxamine or 20 μM EDTA and completely inhibited by 10 μM desferrioxamine or 100 μM EDTA. Inhibition of hemoglobin-catalyzed peroxidation was not accompanied by any changes in the absorbance spectra of hemoglobin, indicating that the heme iron was not withdrawn by the inhibitor. Inhibition of hematin-catalyzed peroxidation by desferrioxamine may have been due to iron chelation and removal, as judged from changes in absorbance spectra. The peroxidation was apparently not dependent on hydrogen peroxide since catalase did not inhibit peroxidation but on the contrary promoted it in some cases.