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NADH oxidation by manganese peroxidase with or without alpha-hydroxy acid
Tetsuya Deguchi1, Masaaki Matsubara, Tomoaki Nishida
1Chemical and Environmental Technology Laboratory, Kobe Steel, Ltd., Japan. te-deguchi@rd.kcrl.kobelco.co.jp
Bioscience, Biotechnology, and Biochemistry
|May 31, 2002
Summary
Manganese peroxidase (MnP) utilizes different reactive oxygen species during NADH oxidation, depending on the substrate. MnP also exhibits distinct catalytic activities beyond Mn(II) oxidation when acetate is present.
Area of Science:
- Biochemistry
- Enzymology
- Oxidative Processes
Background:
- Manganese peroxidase (MnP) is a key enzyme in lignin degradation and other oxidative processes.
- Understanding the reaction mechanisms and active oxygen species involved in MnP catalysis is crucial for various biotechnological applications.
- Previous studies have focused on Mn(II) oxidation, but the role of other substrates and reaction conditions requires further investigation.
Purpose of the Study:
- To investigate the differences in NADH oxidation mechanisms by manganese peroxidase (MnP) using alpha-hydroxy acid and acetate as substrates.
- To identify the specific active oxygen species involved in these distinct reaction pathways.
- To explore potential alternative catalytic activities of MnP beyond Mn(II) oxidation.
Main Methods:
- NADH oxidation assays were performed using MnP in reaction mixtures containing either alpha-hydroxy acid or acetate.
- Enzyme activity was modulated using specific inhibitors like catalase and superoxide dismutase.
- The effect of exogenous hydrogen peroxide (H2O2) on reaction rates was assessed.
- MnP reduction experiments with Mn(II) were conducted to probe for additional catalytic functions.
Main Results:
- NADH oxidation with alpha-hydroxy acid was inhibited by catalase and accelerated by H2O2, suggesting involvement of hydrogen peroxide.
- NADH oxidation with acetate was inhibited by superoxide dismutase and not accelerated by H2O2, indicating a role for superoxide radicals.
- These findings highlight distinct reactive oxygen species mediating MnP activity depending on the reaction substrate.
- MnP reduction experiments with Mn(II) indicated a separate catalytic activity in the presence of acetate, distinct from Mn(II) to Mn(III) oxidation.
Conclusions:
- The reaction environment significantly influences the active oxygen species utilized by manganese peroxidase during NADH oxidation.
- MnP exhibits substrate-dependent mechanisms involving different reactive oxygen species, including H2O2 and superoxide radicals.
- MnP possesses catalytic activities beyond Mn(II) oxidation, particularly when acetate is present in the reaction mixture.