Protection against free radical formation by protein bound iron.

Naturally occurring protein-bound and artificially chelated iron have been evaluated for their catalytic effect in promoting hydroxyl radical (X OH) formation from H2O2 decomposition and on epinephrine autooxidation. Iron bound to ferritin and transferrin did not increase X OH formation or epinephrine autooxidation, whereas iron equivalents of Fe-EDTA considerably augmented those processes. After rigorous removal of contaminating trace iron, X OH can be detected at concentrations of 1.0 microM Fe3+ or 2-5 microM H2O2. Although other forms of iron found physiologically might cause considerable oxidative damage through mechanisms similar to that of Fe-EDTA, our studies indicate considerable mitigation of such toxicity in ferritin and transferrin, which constitute major forms of transport and storage of iron in vivo.