This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anticoagulants and Coagulants, Subject name: Pharmacology
Warfarin acts by - 
Select and explain. 
A. Inhibition of Vitamin K epoxide reductase, B. Inhibition of gamma glutamyl carboxylase, C. Activation of Vitamin K epoxide reductase, D. Activation of gamma glutamyl carboxylase
A: Inhibition of Vitamin K epoxide reductase
Answer: A: Inhibition of Vitamin K epoxide reductase 
Explanation: Ans. is 'a' i.e., Inhibition of Vitamin K epoxide reductase o During g-carboxylation of the coagulant factor II, VII, IX and X in the liver, active vitamin K (Vit K hydroquinone) is oxidized to an epoxide (vit K epoxide).o Vit K epoxide must be reduced to vit K hydroquinone to become active once again (vit K cycle),o Vit K epoxide is reduced to vit K hydroquinone by vit K reductase.o This vit K reductase is inhibited by oral anticoagulants.