Catalytic scavenging of peroxynitrite by isomeric Mn(III) N-methylpyridylporphyrins in the presence of reductants.

摘要: Three isomers of manganese(III) 5,10,15,20-tetrakis(N-methylpyridyl)porphyrin (MnTMPyP) were evaluated for their reaction with peroxynitrite. The Mn(III) complexes reacted peroxynitrite anion rate constants 1.85 × 107, 3.82 106, and 4.33 106 M-1 s-1 at 37 °C MnTM-2-PyP, MnTM-3-PyP, MnTM-4-PyP, respectively, to yield the corresponding oxo−Mn(IV) complexes. Throughout pH range from 5 8.5, MnTM-2-PyP 5-fold faster than other two isomers. could in turn be reduced by glutathione, ascorbate, urate, or oxidize tyrosine. reduction ranged >107 ascorbate 103−104 tyrosine glutathione. Cyclic voltammetry experiments show that there is no significant difference E1/2 Mn(IV)/Mn(III) couple; thus, differential reactivity three isomeric interpreted terms electrostatic steric effects. Micromolar concentrations MnTM-...