Vitamin K

Vitamin K is a group of fat-soluble compounds that enable the activation of proteins involved in blood clotting and bone metabolism. Its main forms are phylloquinone (K1) and menaquinones (K2).

Gamma-carboxylation: A chemical modification that adds a carboxyl group to glutamate residues in proteins. Vitamin K enables this modification, which lets clotting and bone proteins bind calcium.
Phylloquinone: The form of vitamin K found mainly in green plants and vegetable oils. It is the principal dietary form of vitamin K in many diets.
Blood coagulation: The process by which blood forms a clot to limit bleeding after vessel injury. Vitamin K activates several proteins required for normal coagulation.
Vitamin K antagonists: Drugs that reduce vitamin K-dependent protein activation by disrupting vitamin K recycling. They oppose vitamin K activity through its recycling pathway rather than by removing clotting proteins.
Vitamin K cycle: A biochemical pathway that recycles vitamin K after it supports protein carboxylation. This cycle restores vitamin K to its active form after each carboxylation reaction.
Menaquinone: A family of vitamin K compounds distinguished by the length of their side chains. These forms are commonly grouped as vitamin K2 and occur in fermented foods and animal products.
Vitamin K deficiency: A state in which inadequate vitamin K impairs activation of vitamin K-dependent proteins. Deficiency can cause abnormal bleeding, especially in newborns and people with impaired absorption.
Direct oral anticoagulants: Anticoagulant drugs that directly inhibit thrombin or activated factor X. Unlike warfarin, these drugs do not act by blocking vitamin K recycling.
Vitamin K epoxide reductase: An enzyme that recycles vitamin K epoxide into forms usable for protein carboxylation. Warfarin blocks this enzyme, interrupting vitamin K recycling.
Vitamin K1: The common name for phylloquinone, the plant form of vitamin K. This name distinguishes the plant-derived form from menaquinones.

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