Vitamin K is a fat soluble vitamin involved in blood clotting, maintaining bone health & various metabolic reactions in the body. There are different forms of Vitamin K ( commonly referred to as a family of closely related molecules) which are discussed below:
- Vitamin K1(phylloquinone): This is the main dietary form of Vitamin K made by plants. Green & leafy vegetables are a good source of Vitamin K1.
- Vitamin K2( menaquinones): This form of Vitamin is produced by gut bacteria & are found in fermented foods & animal products. There are different molecules called menaquinones under the form of Vitamin K2. These are denoted by MK-4 to MK-13. Bacterias in our intestines product MK-10 & MK-11. MK-4 can be produced by the body without need of gut bacteria. MK-4 is also found in dairy, meat & eggs.
- Vitamin K-3 is a synthetic form of Vitamin K used in animal feed.
Vitamin K is an essential cofactor. We have discussed in our earlier blogs cofactor are enzymes that help in carrying out chemical reactions in our body. Vitamin K is an essential cofactor for a key enzyme that activates various proteins collectively known as Vitamin-K dependent proteins. These play an important role in blood clotting & bone health.
When you cut yourself while cutting vegetables, you may start bleeding however it stops after sometime. Do you know why this happens? After you cut & injure a blood vessel, platelets in your blood vessels come & plug the injured site. Proteins circulating in your bloodstream( called clotting factors) activate each other, thereby leading to production of fibrous protein known as fibrin. Long strands of fibrin form a net that traps more platelets & red blood cells to form a blood clot that prevents bleeding. Clotting factors as discussed above are Vitamin K dependent proteins. Therefore Vitamin K plays an important role in activating these clotting factors & facilitating to form blood clot.
People suffering from Vitamin-K deficiency/low levels of Vitamin K have blood that takes considerable longer period of time to clot.
Besides, a lot of bone related proteins are also vitamin K dependent proteins that should be activated using Vitamin-K. One of the important proteins is osteocalcin. This protein binds calcium & helps to deposit it within the bone- called as bone mineralisation. This helps to strengthen the bone. Another Vitamin-K dependent protein stimulates cells called osteoblasts which lays down foundation for new bone. This essentially means that Vitamin K can potentially reduce risk of Osteoporosis( loss of bone mineral density, which makes bone more susceptible to fracture).
Given that Vitamin K is fat soluble vitamin, it should be absorbed along with fat in the intestines. Vitamin K is then packed with fats in lipoproteins particles & transported in the bloodstream to liver & various other tissues. Vitamin K in our diet is in a form which is inactive. Vitamin K cycle facilitates converting Vitamin K into active form by a process that activates various Vitamin K dependent proteins. This process involves a series of metabolic reactions that allows us to convert inactive Vitamin K from our diet into active Vitamin K. This active Vitamin K is used by GGCX enzyme to activate Vitamin-K dependent protein for blood clotting & maintaining bone health. Vitamin K cycle passes through these stages:
- Inactive dietary vitamin-K is converted into active Vitamin K. This is caused by the VKOR enzyme.
- Active Vitamin K is used as a cofactor by GGCX enzyme. This enzyme activates Vitamin K dependent protein. As a result active Vitamin K hydroquinone is converted into Vitamin K epoxide.
- Vitamin K epoxide is recycled back into inactive Vitamin K. This is carried out by the VKOR enzyme. This recycled vitamin K can go through the similar process
Besides recycling , Vitamin K can also be inactivated & removed from the liver which is done by CYP4F2 enzyme. This enzyme is coded by the CYP4F2 gene. This enzyme acts to remove inactive Vitamin K from the Vitamin K cycle to inactive Vitamin-K. This enzyme helps in regulating excessive accumulation of Vitamin K. If your CYP4F2 gene has T allele, it results in reduced breakdown & inactivation of Vitamin K
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