Which statement correctly lists vitamin K–dependent clotting factors?

Which statement correctly lists vitamin K–dependent clotting factors?

• A. Factor II, VII, IX, and X
• B. Factor VIII and XIII
• C. Factor V and VIII
• D. Factor I and II

Answer: (A)

Vitamin K–dependent gamma-carboxylation is required for a subset of clotting factors to become functional, because it enables these proteins to bind calcium and assemble on phospholipid surfaces during coagulation. The four factors that undergo this modification are II (prothrombin), VII, IX, and X. That makes the list that includes precisely these four the correct one. The other options mix factors that are not vitamin K–dependent (for example, factor VIII is not vitamin K–dependent, nor are V or fibrinogen) or include components that aren’t clotting factors. In practice, deficiencies in vitamin K or warfarin therapy reduce II, VII, IX, and X activity, which underlies the observed effects on coagulation tests.

Vitamin K–dependent gamma-carboxylation is required for a subset of clotting factors to become functional, because it enables these proteins to bind calcium and assemble on phospholipid surfaces during coagulation. The four factors that undergo this modification are II (prothrombin), VII, IX, and X. That makes the list that includes precisely these four the correct one. The other options mix factors that are not vitamin K–dependent (for example, factor VIII is not vitamin K–dependent, nor are V or fibrinogen) or include components that aren’t clotting factors. In practice, deficiencies in vitamin K or warfarin therapy reduce II, VII, IX, and X activity, which underlies the observed effects on coagulation tests.