Superoxide dismutase mimics based on iron in vivo

Novel metal complexes, Fe(II)-tetrakis-N,N,N',N' (2-pyridylmethyl)ethylenediamine(Fe-TPEN) and Fe(III)-tris[N-(2-pyridylmethyl)-2-aminoethyl]amine (Fe-TPAA), catalyzed the dismutation of superoxide, and 0.8 microM Fe-TPEN and 7.5 microM Fe-TPAA were equivalent to 1 unit of superoxide dismutase (SOD) activity in the xanthine oxidase-cytochrome c assay. Addition of serum albumin had no effect on the activities of Fe-TPEN and Fe-TPAA but depressed those of the Cu(salicylate)2 and Cu(diisopropylsalicylate)2 complexes. Both iron complexes blocked the toxic effect of paraquat on Escherichia coli growth and survival without causing induction of SOD. In contrast, this behavior was not seen with other SOD mimics containing copper or manganese. These results support the view that the SOD activities of these iron complexes remain intact in living cells.