A patient with chronic granulomatous disease has a genetic defect in NADPH oxidase. Neutrophils from this patient cannot generate superoxide during the respiratory burst. Which enzyme is directly responsible for the initial generation of superoxide anion from molecular oxygen in normal neutrophils?
- A Myeloperoxidase
- B Superoxide dismutase
- C NADPH oxidase ✓
- D Catalase
Correct answer: C. NADPH oxidase
Explanation
NADPH oxidase (phagocyte oxidase) catalyzes the one-electron reduction of oxygen to superoxide anion (O2.-) using NADPH as the electron donor. This is the first step of the respiratory burst. Myeloperoxidase converts H2O2 to hypochlorous acid. Superoxide dismutase converts superoxide to H2O2. Catalase breaks down H2O2 to water and oxygen.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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