Introduction Catalase activity (2H2O2→2H2O+O2) is crucial to reduce oxidative stress in living body. Numerous studies are reported for catalase mimic based on mononuclear and dinuclear metal complexes. However, these complexes are soluble only in common organic solvent, which limits biochemical application. Herein, we report our recent studies of the new approaches for water-soluble Mn-porphyrin complex as catalase mimic for antioxidative activity. Dinuclear Mn-porphyrin complex (MnPD) is a mimic of manganese catalase having two Mn ions in its active center. The catalase activity of MnPD and its mechanism is investigated in complete aqueous media. The other catalase mimic is a polymer-bound mononuclear Mn-porphyrin complex (Mn-porphyrin / CM-PVIm) as a mimic of heme catalase. Mn-porphyrin is non-covalently attached to a polymer having imidazole groups as acid-base catalyst (CM-PVIm). The effect of the imidazole groups on catalase activity is described. Results and Discussion MnPD exhibited remarkable catalase activity (kCAT=3.3×102 M-1s-1) under physiological conditions, whereas MnM4PyP3P (a half model for MnPD) was inactive. The mechanistic study indicates that high-valent hydroxo Mn(IV) complex is generated during the catalase reaction. Thus, dinucelar structure plays a crucial role for formation of the reactive intermediate. Furthermore, MnPD exhibited significant antioxidative activity in in vivo. Thus, MnPD can be a candidate as catalase mimic for therapeutic antioxidant. Mn-porphyrin/CM-PVIm complex exhibited significant catalase activity under physiological conditions. The stopped-flow analysis indicates that oxo-Mn(V) complex is generated during the catalase reaction. Thus, the acid-base catalytic effect of imidazole plays an important role for formation of the reactive intermediate. Interestingly, the complex composed of Mn-porphyrin with electron-withdrawing structure and CM-PVIm with shorter chain length exhibited highly efficient catalase activity (kCAT=8.5×102 M-1s-1). Our approaches for catalase activity would broaden the scope of the application of Mn-porphyrin in the field of medicinal, coordination and polymer chemistry.

Bioinspired water-soluble Mn-porphyrin complex as catalase mimic for antioxidative activity

254th National Meeting (2017)

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