Vitamin K and Blood Coagulation

• Vitamin K regulates blood coagulation.
• Vitamin K assists the conversion of coagulation factors into mature forms.
• The body cannot control clot formation without vitamin K.
• Production of coagulation factors II, VII, IX, and X requires an enzyme that utilizes vitamin K.
• Vitamin K Cycle: A series of oxidation and reduction reactions that recycle Vitamin K.
• Dietary form of Vitamin K: vitamin K quinone.
• Quinone reductase uses electrons from NADPH to convert vitamin K quinone into vitamin K hydroquinone.
• Vitamin K hydroquinone donates electrons to gamma glutamyl carboxylase.
• Gamma glutamyl carboxylase converts non-functional coagulation factors II, VII, IX, and X into functional forms.
• Vitamin K is oxidized into vitamin K epoxide.
• Vitamin K epoxide receives electrons via epoxide reductase, reverting to vitamin K quinone.
• A single molecule of vitamin K can be reused many times.
• Warfarin inhibits epoxide reductase function, preventing vitamin K recycling, which hinders the activation of Factors II, VII, IX, and X.
• The coagulation cascade initiates via the extrinsic and intrinsic pathways.
• The intrinsic pathway starts when circulating factor XII contacts activated platelets or collagen.
• Activated factor XII activates factor XI, which activates factor IX, which activates factor X.
• Factor X starts the common pathway where it activates factor II, which activates factor I that builds the fibrin mesh.
• Activated factor II also activates factors V, VIII, XI, and XIII.
• Activated factor V acts as a cofactor for X, factor VIII acts as a cofactor for factor IX, and factor XIII helps factor I, fibrin, form crosslinks.
• In the extrinsic pathway, exposed tissue factor activates factor VII, which activates factor X, initiating the common pathway.
• Without vitamin K, the loss of factor VII impairs the extrinsic pathway; loss of factor IX impairs the intrinsic pathway; loss of factor X and II impairs the common pathway.
• Because factors II, VII, IX, and X are utilized in all three pathways, clot formation won’t function properly unless our body properly utilizes vitamin K.

Vitamin K is essential for blood coagulation as it aids in converting coagulation factors into their mature forms. It is required for the production of coagulation factors II, VII, IX, and X. The vitamin K cycle involves oxidation and reduction reactions to recycle Vitamin K, enabling its reuse.