The primary intracellular antioxidant defence against hydrogen peroxide in erythrocytes is:

• A Superoxide dismutase (SOD)
• B Catalase using NADPH
• C Thioredoxin reductase using FADH2
• D Glutathione peroxidase using reduced glutathione (GSH) ✓

Explanation

Glutathione peroxidase reduces H2O2 and lipid hydroperoxides using GSH as reducing substrate, converting GSH to GSSG; GSSG is reconverted to GSH by glutathione reductase using NADPH (supplied by the HMP shunt). SOD converts superoxide to H2O2. Catalase also degrades H2O2 but glutathione peroxidase is the primary erythrocyte mechanism. Thioredoxin uses NADPH but is secondary in RBCs.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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