In inflammatory tissue, nitric oxide released by inducible nitric oxide synthase reacts rapidly with superoxide radical to generate a potent nitrating species that tyrosine-nitrates proteins and damages DNA. Which species is formed?

• A Lipid hydroperoxide
• B Hypochlorous acid
• C Hydrogen peroxide
• D Peroxynitrite ✓

Explanation

The diffusion-limited reaction between nitric oxide and superoxide yields peroxynitrite (ONOO-), which protonates to peroxynitrous acid and decomposes into highly damaging nitrogen dioxide and hydroxyl radical-like intermediates. Peroxynitrite nitrosates protein tyrosines to 3-nitrotyrosine, a marker of nitrosative stress seen in sepsis and atherosclerosis. Hypochlorous acid comes from myeloperoxidase acting on chloride, and hydrogen peroxide arises from superoxide dismutation, neither involving nitric oxide.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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