Vitamin K in its coenzyme form is regenerated by which enzyme?
(A) Glutathione reductase (B) Pyruvate carboxylase (C) Dihydrofolate reductase (D) Epoxide reductase
(D) Vitamin K - Vitamin K hydroquinone is oxidized to the epoxide Epoxide activates a glutamate residue in the protein substrate to a carbanion, which reacts nonenzymically with carbon dioxide to form g-carboxyglutamate. Vitamin K epoxide is reduced to the quinone by an epoxide reductase, and the quinone is reduced to the active hydroquinone by Vitamin K reductase. Dicumarol & warfarin inhibits the enzyme (reductase) that conves epoxide to active Vitamin K (hydroquinone).