<prompt> Vitamin K is a cofactor in:CarboxylationHydroxylationDeaminationHydrolysis  <response>: Ans. A CarboxylationRef: Katzung 10e p549, 550; KDT 8e p667Vitamin 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. 