Vitamin K acts as a cofactor for gamma-glutamyl carboxylase in the liver. Which set of coagulation factors undergoes this post-translational modification, and what does carboxylation enable?
- A Factors II, VII, IX, X; enables calcium binding to phospholipid membranes via Gla domains ✓
- B Factors I, V, VIII, XIII; enables fibrin polymerization
- C Factors II, V, X, XI; enables thrombin receptor binding
- D Factors VII, VIII, IX, XI; enables binding of tissue factor
Correct answer: A. Factors II, VII, IX, X; enables calcium binding to phospholipid membranes via Gla domains
Explanation
The vitamin K dependent factors are II (prothrombin), VII, IX and X, along with proteins C and S. Gamma-carboxylation of specific glutamate residues creates Gla domains that chelate calcium ions, allowing these zymogens to dock on phosphatidylserine bearing membrane surfaces where coagulation complexes assemble. Factors I, V, VIII and XIII are soluble cofactors or substrates and are not vitamin K dependent.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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