bones are the main sources of vitamin k.
what are the main sources of vitamin k?
bones
vitamin k, also known as phylloquinone, is made by plants, and is found in highest amounts in green leafy vegetables because it is directly involved in photosynthesis. it may be thought of as the plant form of vitamin k. it is active as a vitamin in animals and performs the classic functions of vitamin k, including its activity in the production of blood-clotting proteins. animals may also convert it to vitamin k.
vitamin k
within the cell, vitamin k undergoes electron reduction to a reduced form called vitamin k hydroquinone, catalyzed by the enzyme vitamin k epoxide reductase (vkor). another enzyme then oxidizes vitamin k hydroquinone to allow carboxylation of glu to gla; this enzyme is called gamma-glutamyl carboxylase or the vitamin k-dependent carboxylase. the carboxylation reaction only proceeds if the carboxylase enzyme is able to oxidize vitamin k hydroquinone to vitamin k epoxide at the same time. the carboxylation and epoxidation reactions are said to be coupled. vitamin k epoxide is then reconverted to vitamin k by vkor. the reduction and subsequent reoxidation of vitamin k coupled with carboxylation of glu is called the vitamin k cycle. humans are rarely deficient in vitamin k because, in part, vitamin k is continuously recycled in cells.
vitamin k