Boning Up on Vitamin K

The importance of vitamin K, phylloquinone (K1) and menaquinones (MKn), extends beyond the antihemorrhagic factor identified in the late 1930s. Vitamin K, in either form, participates as a cofactor for a specific unique enzyme, γ-glutamyl carboxylase. The reduced form of the vitamin in the presence of CO₂ converts the glutamate moieties of several coagulation proteins to γ-carboxyglutamate amino acids. The resulting modified proteins act as calcium-binding proteins, which stimulate the coagulati…