Peroxynitrite (ONOO-), a reactive nitrogen species implicated in endothelial dysfunction and neurodegeneration, is formed by the near diffusion-limited reaction of nitric oxide with which species?

• A Hydrogen peroxide
• B Lipid peroxyl radical
• C Hydroxyl radical
• D Superoxide anion ✓

Explanation

Nitric oxide reacts with superoxide anion at a rate approaching the diffusion limit to form peroxynitrite, which nitrates tyrosine residues (forming nitrotyrosine), damages DNA, and inhibits mitochondrial enzymes. This reaction also explains how excess superoxide reduces NO bioavailability in hypertension and atherosclerosis. Hydrogen peroxide does not react directly with NO to form ONOO-, and the hydroxyl radical arises downstream from peroxynitrite decomposition, not upstream.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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