Vitamin K-dependent coagulation factors (Factor II, Factor VII, Factor IX, Factor X, Protein C, and Protein S) (VKDFs)

The Vitamin K-dependent coagulation factors are a group of liver-synthesized proteins essential for the regulation of blood clotting, consisting of pro-coagulant factors II (prothrombin), VII, IX, and X, as well as the anticoagulant proteins C and S [1][3]. These proteins are characterized by a unique N-terminal domain containing gamma-carboxyglutamic acid (Gla) residues, which are formed through a Vitamin K-dependent post-translational modification [2][4]. This modification is vital as it allows the proteins to bind calcium ions and anchor to negatively charged phospholipid surfaces on activated platelets, a prerequisite for their enzymatic activation in the coagulation cascade [2][4]. In clinical medicine, these factors are the primary targets of Vitamin K antagonists like warfarin, which are widely prescribed to prevent stroke in atrial fibrillation and to treat venous thromboembolism [5]. Because these drugs interfere with the recycling of Vitamin K, they lead to the production of under-carboxylated, inactive forms of these factors [1][6]. Due to the narrow therapeutic index and the fact that these drugs affect both pro- and anti-coagulant pathways, patients require frequent monitoring of the International Normalized Ratio (INR) to balance efficacy against the significant risk of hemorrhage [1][5].

Other names

Vitamin K-dependent proteinsGla-domain containing coagulation factorsProthrombin complex factorsVitamin K-dependent clotting factors

Vitamin K antagonists (VKAs) inhibit the enzyme Vitamin K epoxide reductase (VKORC1), which is responsible for regenerating reduced Vitamin K from its epoxide form [1][6]. Reduced Vitamin K is an essential cofactor for the enzyme gamma-glutamyl carboxylase, which adds carboxyl groups to glutamic acid residues on factors II, VII, IX, X, and proteins C and S [2][4]. By preventing this modification, VKAs lead to the synthesis of dysfunctional coagulation factors that cannot bind calcium or phospholipid membranes, effectively slowing the formation of fibrin clots [1][2].