Superoxide dismutase (SOD) is a primary antioxidant enzyme that converts superoxide radicals to hydrogen peroxide. The subsequent detoxification of hydrogen peroxide in hepatocytes is primarily accomplished by:

• A Xanthine oxidase, regenerating uric acid
• B Catalase and glutathione peroxidase, using NADPH-derived electrons ✓
• C Vitamin C, directly reducing H2O2 to water
• D Mitochondrial complex II accepting electrons from H2O2

Explanation

Hydrogen peroxide generated by SOD is detoxified by two enzymatic systems in hepatocytes. Catalase, concentrated in peroxisomes, directly dismutates H2O2 to water and oxygen (2H2O2 → 2H2O + O2). Glutathione peroxidase uses reduced glutathione (GSH) as an electron donor to reduce H2O2; the resulting oxidized glutathione (GSSG) is regenerated to GSH by glutathione reductase using NADPH, which is supplied by the HMP shunt. This dual system is essential because unchecked H2O2 participates in Fenton chemistry to generate hydroxyl radicals.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

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