The Vitamin K Cycle and Blood Clotting

🌱 Perhaps best known in relation to blood clotting, as many people on warfarin are told to reduce their green leafy veggies because the K1 they contain, can be antagonistic to the drug's effect by activating blood clotting proteins. If you cut yourself and a scab forms, you can thank vitamin K...

🌱 Vitamin K is efficiently recycled in the body through the aptly named vitamin K cycle. We absorb vitamin K from food in its inactive form, called quinone. The inactive quinone is activated by gaining electrons (a process called reduction) to become hydroquinone thanks to the enzyme Vitamin K Epoxide Reductase (VKOR). The hydroquinone can then work with gamma-glutamyl carboxylase (GGCX) enzyme as its cofactor to activate coagulation proteins (Factor II, VII, IX, X). During this activation process, the hydroquinone loses electrons (a process called oxidation) and which is recycled back to quinone, ensuring efficient recycling of vitamin K. GGCX binds to glutamic acid residues which are found on the coagulation proteins. The addition of an extra acid group turns the glutamic acid proteins into gammacarboxy-glutamic acid, which we can thankfully refer to as Gla proteins! These Gla proteins bind to calcium ions, which help localise clotting factors to the site of injury. Calcium and vitamin K is also involved in bone formation, but more on that another time!