Vitamin K

Vitamin K is not a single molecular target but rather a family of structurally related fat-soluble vitamers essential for human health. The two main natural forms are vitamin K1 (phylloquinone, also called phytonadione)—primarily found in green leafy vegetables—and vitamin K2 (menaquinones), which are produced by bacteria and found in animal-based foods. Vitamin K acts as an essential cofactor for the enzyme gamma-glutamyl carboxylase, enabling the post-translational γ-carboxylation of glutamic acid residues on specific proteins. This modification is critical for activating several blood-clotting factors as well as proteins involved in bone mineralization and inhibition of vascular calcification. Deficiency leads to impaired blood clotting with increased bleeding risk and may contribute to osteoporosis or pathological soft tissue calcification. While vitamin K itself is not considered a therapeutic target like an enzyme or receptor, it plays a crucial role in modulating targets such as clotting factors through its biochemical activity. Drugs like warfarin act by inhibiting the recycling of active vitamin K via blockade of the enzyme VKORC1 (vitamin K epoxide reductase complex subunit 1). Monitoring prothrombin time helps assess both deficiency states and efficacy/safety during anticoagulant therapy. Because "Vitamin K" refers to a nutrient group rather than a discrete molecular target or receptor/protein entity typically used in drug discovery or pharmacology databases, it should be flagged as incorrect if used where only canonical targets are expected.

Other names

PhylloquinonePhytonadioneVitamin K1Menaquinone (Vitamin K2)Menadione (Vitamin K3)antihemorrhagic vitaminalpha-PhylloquinoneFitomenadionaPhytomenadione

Cofactor for gamma-glutamyl carboxylase in the post-translational modification of clotting factors and other proteins