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
[{'content': 'Vitamin K is a cofactor in: \nSelect and explain. \nA. Carboxylation, B. Hydroxylation, C. Deamination, D. Hydrolysis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (A) Carboxylation(Ref: Katzung 10/e p549, 550; KDT 8/e p667)Vitamin K is involved in activation of various clotting factors (like II, VII, IX and X) as well as anti-clotting proteins (like protein C and S). It carries out the final step in activation of these factors i.e. gamma carboxylation of glutamate residues in these factors.', 'role': 'assistant'}]