Abstract
Vitamin K belongs to the group of the fat-soluble vitamins and there are three forms of Vitamin K - K1, K2, K3. Vitamin K acts as cofactor of post-translational carboxylation of glutamic acid to γ-carboxyglutamic acid, which is important for binding of calcium ions by coagulation factors, protein C and protein S.
It participates in functions of other proteins interacting with calcium ions e.g. osteocalcin and matrix Gla protein. Vitamin K1 plays a role especially in blood coagulation while Vitamin K2 affects bone remodeling and calcium homeostasis.
An anticancer effect is described at all of forms of Vitamin K, however the best results in vitro and in vivo were described by Vitamin K3 for now. Daily intake of Vitamin K1 in a Western diet is sufficient for blood coagulation, whereas daily intake of Vitamin K2 is insufficient for covering carboxylation of Vitamin K dependent proteins.
Insufficient carboxylation of Vitamin K dependent proteins is associated with higher risk of osteoporosis fracture's occurrence, and excessive calcification of vascular walls due to calcium paradox. Vitamin K is absorbed from the gastrointestinal tract in the presence of bile salts and pancreatic lipase, and in plasma is transported by lipoproteins.
The reference range of Vitamin K1 can be found in the literature whereas the reference range of Vitamin K2 has been not published. Vitamin K can be determined by chromatografic methods.