Warfarin produces its anticoagulant effect by inhibiting which enzyme?

• A Thrombin (factor IIa)
• B Gamma-glutamyl carboxylase
• C Factor Xa
• D Vitamin K epoxide reductase ✓

Explanation

Warfarin inhibits vitamin K epoxide reductase (VKORC1), preventing regeneration of reduced vitamin K. This impairs gamma-carboxylation of glutamate residues on factors II, VII, IX and X and proteins C and S, so they cannot bind calcium and phospholipid membranes. Gamma-glutamyl carboxylase is the downstream enzyme that needs vitamin K as cofactor, but warfarin does not inhibit it directly, which is what kills option B. The effect is on synthesis, not on circulating factors.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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