Within neutrophil phagolysosomes, myeloperoxidase acts on hydrogen peroxide in the presence of which halide ion to generate the most potent bactericidal oxidant of the respiratory burst?

• A Iodide, forming iodine radicals
• B Chloride, forming hypochlorous acid ✓
• C Fluoride, forming hypofluorous acid
• D Bromide, forming bromamine

Explanation

Myeloperoxidase uses H2O2 and chloride ion to form hypochlorous acid (HOCl), the major microbicidal oxidant of neutrophils. HOCl further reacts with amines to form chloramines, extending its killing activity. Chloride is abundant in plasma at roughly 100 mmol/L, making it the physiologically relevant substrate despite MPO being able to oxidise other halides in vitro. This abundance is the fact that eliminates iodide and bromide as answers.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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