Vitamin K

• Vitamin K activity can be supplied by phylloquinone (vitamin K₁; found in plants), menaquinone (vitamin K₂; found in animal tissues and synthesized by intestinal bacteria), or the synthetic form, menadione (vitamin K₃).
• Vitamin K functions in the biosynthesis of  blood clotting factors (factors II, VII, IX and X).  This function involves vitamin K as a cofactor in the carboxylase which converts the glutamate residues of the precursor clotting factor proteins (posttranslationally) to gamma-carboxyglutamate residues.  As a consequence of this role, vitamin K deficiency results in hemorrhagic syndromes.