Question:medium
Which of the following clotting factors in a patient on warfarin therapy would have decreased gamma-carboxyglutamate residues?
Which of the following clotting factors in a patient on warfarin therapy would have decreased gamma-carboxyglutamate residues?
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Only the 2, 7, 9, 10 (and proteins C, S, Z) group is undercarboxylated by warfarin.
Updated On: Jun 23, 2026
- Factor 2
- Factor 11
- Tissue factor
- Factor 5
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The Correct Option is A
Solution and Explanation
Use the classic mnemonic for vitamin K-dependent factors: 1972 (factors 10, 9, 7, 2) plus proteins C, S, and Z. Warfarin starves the gamma-carboxylase of reduced vitamin K, so these factors leave the liver undercarboxylated, meaning fewer gamma-carboxyglutamate (Gla) residues. Scan the options against the list, and only Factor 2 (prothrombin) qualifies, so option (a) is correct.
The Gla residues are the calcium-binding hooks that anchor the factor to platelet phospholipid membranes; without them the factor cannot work normally even though protein is present. Factor 11 (option b) and Factor 5 (option d) are not vitamin K-dependent, so warfarin does not change their carboxylation. Tissue factor (option c) is a transmembrane initiator of coagulation, not a Gla protein. Hence Factor 2 is the answer.
Ref: Vitamin K-dependent carboxylation biochemistry.
The Gla residues are the calcium-binding hooks that anchor the factor to platelet phospholipid membranes; without them the factor cannot work normally even though protein is present. Factor 11 (option b) and Factor 5 (option d) are not vitamin K-dependent, so warfarin does not change their carboxylation. Tissue factor (option c) is a transmembrane initiator of coagulation, not a Gla protein. Hence Factor 2 is the answer.
Ref: Vitamin K-dependent carboxylation biochemistry.
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