A 32-year-old man is brought to the emergency department after ingesting antifreeze. Laboratory studies reveal high anion gap metabolic acidosis. Urine microscopy shows monohydrate calcium oxalate crystals. The toxic metabolite responsible for this crystal formation is produced by which enzyme?
- A Alcohol dehydrogenase ✓
- B Aldehyde dehydrogenase
- C Xanthine oxidase
- D Cytochrome P450 2E1
Correct answer: A. Alcohol dehydrogenase
Explanation
Ethylene glycol is metabolized by alcohol dehydrogenase to glycoaldehyde, then to glycolic acid, glyoxylic acid, and oxalic acid. Oxalic acid binds calcium to form calcium oxalate crystals in kidneys and other tissues. Alcohol dehydrogenase is the rate-limiting first enzyme. Fomepizole works by inhibiting this enzyme, blocking toxic metabolite formation. Distractor D (CYP2E1) is more relevant to ethanol and paracetamol metabolism.
Reference: Goldfrank's Toxicologic Emergencies, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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