Superoxide dismutase (SOD) converts superoxide radical to hydrogen peroxide. The subsequent detoxification of H2O2 in erythrocytes primarily involves which enzymatic system?

• A Catalase using NADH as electron donor
• B Thioredoxin reductase using FAD as prosthetic group
• C Myeloperoxidase converting H2O2 to hypochlorous acid for detoxification
• D Glutathione peroxidase (GPx) using reduced glutathione (GSH) as electron donor, with GSH regenerated by glutathione reductase using NADPH ✓

Explanation

In erythrocytes, H2O2 is detoxified primarily by glutathione peroxidase (GPx), which catalyses: H2O2 + 2 GSH → 2 H2O + GSSG (oxidised glutathione). Oxidised GSSG is regenerated to GSH by glutathione reductase: GSSG + NADPH + H+ → 2 GSH + NADP+. NADPH is supplied by the HMP shunt (glucose-6-phosphate dehydrogenase reaction). In G6PD deficiency, reduced NADPH impairs GSH regeneration, allowing H2O2 and lipid peroxides to accumulate causing haemolysis under oxidative stress. Catalase is also present in red blood cells and uses H2O2 directly without cofactors; however, GPx is the dominant system for lower H2O2 concentrations. Myeloperoxidase uses H2O2 to generate hypochlorite as an antimicrobial weapon in neutrophils, not for detoxification.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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