Within the phagolysosome, hydrogen peroxide generated by the respiratory burst is converted by a heme enzyme into hypochlorous acid, the major microbicidal agent of neutrophils. This enzyme uses which halide ion as substrate?

• A Fluoride
• B Bromide
• C Iodide
• D Chloride ✓

Explanation

Myeloperoxidase, a heme-containing enzyme abundant in neutrophil azurophilic granules, catalyzes the reaction of hydrogen peroxide with chloride ion to form hypochlorous acid (HOCl). HOCl is a potent oxidant that halogenates and oxidizes microbial proteins, making it the principal killing mechanism even though it accounts for only a fraction of consumed oxygen. Bromide can substitute weakly in vitro, but chloride is the physiological substrate used in vivo.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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