Which of the following coagulation factors is synthesized in the liver and requires vitamin K for its γ-carboxylation?

Explanation

## Vitamin K-Dependent Coagulation Factors **Key Point:** Vitamin K is essential for the post-translational γ-carboxylation of glutamic acid residues in coagulation factors, enabling them to bind calcium and phospholipid surfaces. ### The Vitamin K-Dependent Factors ("PIVKA") **Mnemonic:** **PIVKA** = **P**rothrombin, **I**ntermediate factors, **V**itamin K, **K**-dependent factors, **A**ll four are: - **Factor II** (Prothrombin) - **Factor VII** - **Factor IX** - **Factor X** ### Why Factor VII is Correct Factor VII is one of the four vitamin K-dependent factors synthesized in the liver. Without adequate vitamin K, these factors cannot be properly γ-carboxylated and remain non-functional (PIVKA — Proteins Induced by Vitamin K Absence). ### Comparison Table: Coagulation Factor Origins & Cofactors | Factor | Vitamin K-Dependent | Synthesized in Liver | Requires Cofactor | | --- | --- | --- | --- | | Factor II | ✓ | ✓ | Ca²⁺, PL | | Factor V | ✗ | ✓ | Ca²⁺, PL | | Factor VII | ✓ | ✓ | Ca²⁺, PL | | Factor VIII | ✗ | Endothelium | vWF | | Factor IX | ✓ | ✓ | Ca²⁺, PL | | Factor X | ✓ | ✓ | Ca²⁺, PL | | Factor XI | ✗ | Liver | — | **High-Yield:** Warfarin and vitamin K deficiency both impair factors II, VII, IX, and X. Factor VII has the shortest half-life (~6 hours), so PT (which measures Factor VII) is the first to prolong in vitamin K deficiency. **Clinical Pearl:** In newborns, vitamin K prophylaxis is given to prevent hemorrhagic disease of the newborn (HDNB), which results from transient vitamin K deficiency and impaired synthesis of these four factors.