menaquinone-6 and coumarin

Vitamin K is a collective term for lipid-like naphthoquinone derivatives synthesized only in eubacteria and plants and functioning as electron carriers in energy transduction pathways and as free radical scavengers maintaining intracellular redox homeostasis. Paradoxically, vitamin K is a required micronutrient in animals for protein posttranslational modification of some glutamate side chains to gamma-carboxyglutamate. The majority of gamma-carboxylated proteins function in blood coagulation. Vitamin K shuttles reducing equivalents as electrons between two enzymes: VKORC1, which is itself reduced by an unknown ER lumenal reductant in order to reduce vitamin K epoxide (K>O) to the quinone form (KH2); and gamma-glutamyl carboxylase, which catalyzes posttranslational gamma-carboxylation and oxidizes KH2 to K>O. This article reviews vitamin K synthesis and the vitamin K cycle, outlines physiological roles of various vitamin K-dependent, gamma-carboxylated proteins, and summarizes the current understanding of clinical phenotypes caused by genetic mutations affecting both enzymes of the vitamin K cycle.

Topics: Animals; Blood Coagulation; Calcium; Carbon-Carbon Ligases; Coumarins; Homeostasis; Humans; Mixed Function Oxygenases; Osteoporosis; Vitamin K; Vitamin K 1; Vitamin K 2; Vitamin K Epoxide Reductases

Topics: Antifibrinolytic Agents; Coumarins; Dicumarol; Hemostatics; Humans; Hypoprothrombinemias; Naphthoquinones; Prothrombin; Retinoids; Vitamin K; Vitamin K 1; Vitamin K 2