The oxidative reactivity of three manganese (III) porphyrin complexes with hydrogen peroxide and nitrite towards catalytic nitration of protein tyrosine.

Understanding the toxicological properties of MnIII-porphyrins (MnTPPS, MnTMPyP or MnTBAP) can provide important biochemical rationales in developing them as the therapeutic drugs against protein tyrosine nitration induced inflammation diseases. Here, we present a comprehensive understanding of the pH-dependent redox behaviors of these MnIII-porphyrins and their structural effects on catalyzing bovine serum albumin (BSA) nitration in the presence of H2O2 and NO2-. It was found that both MnTPPS and MnTBAP stand out in catalyzing BSA nitration at physiologically close condition (pH 8), yet they are less effective at pH 6 and 10. MnTMPyP was shown no ability to catalyze BSA nitration under all tested pHs (pH 6, 8 and 10). The kinetics and active intermediate determination through electrochemistry method revealed that both the pH-dependent redox behavior of the central metal cation and the antioxidant capability of porphin derivative contribute to the catalytic activities of three MnIII-porphyrins in BSA nitration in the presence of H2O2/NO2-. These comprehensive studies on the oxidative reactivity of MnIII-porphyrins towards BSA nitration may provide new clues for searching the manganese based therapeutic drugs against the inflammation related diseases.