Metronidazole is used in the treatment of Giardia lamblia infection. In this protozoan, the activation of metronidazole differs from its activation in anaerobic bacteria because Giardia utilizes which electron donor for nitro group reduction?

• A NADH dehydrogenase
• B Xanthine oxidase
• C Cytochrome P450 reductase
• D Pyruvate:ferredoxin oxidoreductase (PFOR) ✓

Explanation

Giardia and other anaerobic protozoa use pyruvate:ferredoxin oxidoreductase (PFOR) to generate reduced ferredoxin, which then reduces metronidazole's nitro group to its active radical form. This enzyme system is analogous to the electron transport chain used by anaerobic bacteria. Options A, C, and B are not involved in metronidazole activation in protozoa.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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