The reaction and why it matters
Gamma-glutamyl carboxylase uses reduced vitamin K to convert specific glutamate residues on target proteins into gamma-carboxyglutamate (Gla). The two adjacent carboxyl groups of Gla chelate calcium, and calcium binding is what attaches the protein to the phospholipid surface of activated platelets. Without that attachment the clotting cascade cannot assemble on the membrane, so the factors are present in plasma but functionally inactive.
Proteins whose function depends on this modification
- Prothrombin (factor II)
- Factor VII
- Factor IX
- Factor X
- Protein C and protein S, which regulate the cascade
What deficiency looks like
Because the factors are synthesized but nonfunctional, the prothrombin time is prolonged and bleeding is the dominant sign: easy bruising, bleeding gums, epistaxis, and in severe cases gastrointestinal or intracranial hemorrhage. The short half-lives of the affected factors mean bleeding appears faster than the skeletal changes of vitamin D deficiency.
Why warfarin works here
Vitamin K epoxide reductase recycles the oxidized vitamin K back to its reduced form. Warfarin inhibits this enzyme, so it depletes reduced vitamin K and reproduces the same functional defect in the clotting factors that dietary deficiency produces.