Phytomenadione, also known as vitamin K1 or phylloquinone, is a vitamin found in food and used as a dietary supplement.[1][2] As a supplement it is used to treat certain bleeding disorders.[2] This includes warfarin overdose, vitamin K deficiency, and obstructive jaundice.[2] It is also recommended to prevent and treat vitamin K deficiency bleeding in infants.[2] Use is typically recommended by mouth, intramuscular injection or injection under the skin.[2] When given by injection benefits are seen within two hours.[2] Many countries in the world choose intramuscular injections in newborn to keep them safe from severe bleeding (VKDB). It is considered a safe treatment and saves many children from death and severe neurologic deficit every year.[3]
Side effects when given by injection may include pain at the site of injection.[2] Severe allergic reactions may occur when it is injected into a vein or muscle, but this has mainly happened when large doses of a certain type of supplement containing castor oil were given intravenously.[4] Use during pregnancy is considered safe,[5] use is also likely okay during breastfeeding.[6] It works by supplying a required component for making a number of blood clotting factors.[2] Found sources include green vegetables, vegetable oil, and some fruit.[7]
Phytomenadione was first isolated in 1939.[8] In 1943 Edward Doisy and Henrik Dam were given a Nobel Prize for its discovery.[8] It is on the World Health Organization's List of Essential Medicines.[9]
Terminology
Phytomenadione is often also called phylloquinone, vitamin K,[10] or phytonadione.
A stereoisomer of phylloquinone is called vitamin k1 (note the difference in capitalization).[citation needed]
Chemistry
Vitamin K is a fat-soluble vitamin that is stable in air and moisture but decomposes in sunlight.[11] It is a polycyclic aromatic ketone, based on 2-methyl-1,4-naphthoquinone, with a 3-phytyl substituent. It is found naturally in a wide variety of green plants, particularly in leaves, since it functions as an electron acceptor during photosynthesis, forming part of the electron transport chain of photosystem I.[12][13]
Biological function
The best-known function of vitamin K in animals is as a cofactor in the formation of coagulation factors II (prothrombin), VII, IX, and X by the liver. It is also required for the formation of anticoagulant factors protein C and S. It is commonly used to treat warfarin toxicity, and as an antidote for coumatetralyl.
Vitamin K is required for bone protein formation.
Biosynthesis
Vitamin K1 is synthesized from chorismate, a compound produced from shikimate via the shikimate pathway. The conversion of chorismate to vitamin K1 comprises a series of nine steps:[14][15]
- Chorismate is isomerized to isochorismate by isochorismate synthase, or MenF (menaquinone enzyme).
- Addition of 2-oxoglutarate to isochorismate by PHYLLO, a multifunctional protein comprising three different enzymatic activities (MenD, H, and C).
- Elimination of pyruvate by PHYLLO.
- Aromatization to yield o-succinyl benzoate by PHYLLO.
- O-succinylbenzoate activation to corresponding CoA ester by MenE.
- Naphthoate ring formation by naphthoate synthase (MenB/NS).
- Thiolytic release of CoA by a thioesterase (MenH).
- Attachment of phytol chain to the naphthoate ring (MenA/ABC4).
- Methylation of the precursor at position 3 (MenG).
Vitamin K1 is required for plant photosynthesis, where it participates in the Photosystem I electron transport chain. As a result, it is rich in leaves.
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