During ischemia, ATP is degraded to hypoxanthine. Upon reperfusion, xanthine oxidase catalyzes the conversion of hypoxanthine to xanthine, generating a specific reactive oxygen species. Which molecule is the initial ROS produced in this reaction?
- A Hydrogen peroxide
- B Superoxide ✓
- C Hydroxyl radical
- D Peroxynitrite
Correct answer: B. Superoxide
Explanation
Xanthine oxidase uses molecular oxygen as an electron acceptor during the oxidation of hypoxanthine to xanthine, producing superoxide (O2•−) as the initial reactive oxygen species. Hydrogen peroxide is subsequently formed by superoxide dismutation. This mechanism is central to reperfusion injury.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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