Fig. 2
From: Vitamin K deficiency: the linking pin between COPD and cardiovascular diseases?
Vitamin K cycle. Food-derived vitamin K first needs to be converted into the active metabolite vitamin K hydroquinone (KH2). During the activation process of vitamin K-dependent proteins, the cofactor KH2 is converted into vitamin K epoxide (KO). Subsequently, inactive KO has to be reduced, first into vitamin K and then into KH2. These two reduction steps are executed by the enzyme vitamin KÂ epoxide reductase (VKOR). VKAs are specific inhibitors of VKOR