Chemistry
Vitamin K is a fat-soluble vitamin that is stable in air and moisture but decomposes in sunlight. 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. 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:
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).
Immerse in 1N sodium hypochlorite (20,000 parts per million available chlorine) for 1 hour; transfer instruments to water; heat in a gravity-displacement autoclave at 121 °C for 1 hour; clean; and then perform routine sterilization processes. Immerse in 1N sodium hydroxide or sodium hypochlorite (20,000 parts per million available chlorine) for 1 hour; remove and rinse in water, then transfer to an open pan and heat in a gravity-displacement (121 °C) or in a porous-load (134 °C) autoclave for 1 hour; clean; and then perform routine sterilization processes.134 °C (273 °F) for 18 minutes in a pressurized steam autoclave has been found to be somewhat effective in deactivating the agent of disease. Ozone sterilization is currently being studied as a potential method for prion denaturation and deactivation. Other approaches being developed include thiourea-urea treatment, guanidinium chloride treatment, and special heat-resistant subtilisin combined with heat and detergent. A method sufficient for sterilizing prions on one material may fail on another.Renaturation of a completely denatured prion to infectious status has not yet been achieved; however, partially denatured prions can be renatured to an infective status under certain artificial conditions. Degradation resistance in nature
Overwhelming evidence shows that prions resist degradation and persist in the environment for years, and proteases do not degrade them. Experimental evidence shows that unbound prions degrade over time, while soil-bound prions remain at stable or increasing levels, suggesting that prions likely accumulate in the environment.