Molybdenum is an essential ultratrace element incorporated into a pterin-based cofactor. Which pair of human enzymes depends on this molybdenum cofactor?

• A Tyrosinase and dopamine beta-hydroxylase
• B Superoxide dismutase and catalase
• C Alcohol dehydrogenase and carbonic anhydrase
• D Xanthine oxidase and sulfite oxidase ✓

Explanation

Molybdenum sits in a pterin cofactor shared by xanthine oxidase/dehydrogenase, sulfite oxidase and aldehyde oxidase. Inherited molybdenum cofactor deficiency therefore produces sulfite accumulation with severe neonatal neurological injury. Option A lists copper-dependent enzymes, option C lists zinc-dependent enzymes, and option B lists antioxidant enzymes using copper-zinc, manganese and iron respectively, so each distractor is killed by knowing its true metal.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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