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Reactions of hypochlorite with catalase
1Department of Biochemistry, Duke University Medical Center, Durham, NC 27710.
Biochimica Et Biophysica Acta
|August 31, 1988
Summary
Hypochlorous acid (HOCl) rapidly inactivates catalase, an enzyme crucial for managing hydrogen peroxide. While some activity is restored by hydrogen peroxide (H2O2), ethanol enhances this recovery, suggesting complex enzyme interactions.
Area of Science:
- Biochemistry
- Enzymology
- Oxidative Stress
Background:
- Catalase (hydrogen-peroxide: hydrogen-peroxide oxidoreductase, EC 1.11.1.6) is a vital enzyme protecting cells from oxidative damage by decomposing hydrogen peroxide (H2O2).
- Hypochlorous acid (HOCl), a reactive oxygen species, is known to interact with and potentially inactivate enzymes.
Purpose of the Study:
- To investigate the inactivation mechanism of catalase by HOCl/OCl-.
- To explore the reversibility of HOCl-induced catalase inactivation and the role of H2O2 and ethanol in this process.
Main Methods:
- Enzyme activity assays were performed to quantify catalase inactivation and recovery.
- Visible absorption spectroscopy was used to monitor spectral changes in catalase upon HOCl exposure.
- Dithionite was employed to assess spectral reversibility.
Main Results:
- HOCl/OCl- rapidly inactivated catalase.
- A slow, partial recovery of catalase activity was observed upon subsequent H2O2 exposure.
- Ethanol significantly accelerated the H2O2-mediated restoration of catalase activity.
- HOCl induced biphasic changes in catalase's visible absorption spectrum, partially reversed by dithionite.
Conclusions:
- A reaction scheme involving axial ligation of HOCl to the heme iron of catalase, followed by O-Cl bond cleavage, is proposed to explain the observed inactivation and spectral changes.
- The findings suggest a complex interplay between HOCl, H2O2, and catalase, with potential implications for understanding oxidative stress mechanisms in biological systems.