Rapid decomposition of peroxynitrite by manganese porphyrin-antioxidant redox couples

Mn(III)TMPyP reacts rapidly with the toxic oxidant peroxynitrite (ONOO−) to generate an oxoMn(IV) species, but Mn(III)TMPyP is not catalytic for ONOO− decomposition due to the slow reduction of oxoMn(IV) back to the Mn(III) oxidation state. However, when redox-coupled with biological antioxidants that efficiently reduce oxoMn(IV), Mn(III)TMPyP is transformed into an efficient “peroxynitrite reductase.”