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Changes in phylloquinone epoxidase activity related to prothrombin synthesis and microsomal clotting activity in the rat.
The oxidation of phylloquinone to the 2,3-epoxide (by phylloquinone epoxidase) was studied in liver from control and warfarin-resistant rats. The reaction requires microsomal fraction, soluble protein, a heat-stable soluble factor and O(2). It is not inhibited by CO or CN(-). Epoxidase activity was stimulated if plasma prothrombin was lowered either by anticoagulants or the absence of vitamin K. The activity of the enzyme rapidly returned to normal values after the administration of vitamin K to hypoprothrombinaemic rats. These differences in the activity of the enzyme occur in the microsomal fraction and not the cytosol. A thrombin-generating polypeptide that accumulates in microsomal fraction of hypothrombinaemic rats correlated directly with epoxidase activity. These data support the view that enzymic interconversion of phylloquinone and its 2,3-epoxide participates in the biological activity of vitamin K.
PMID: 4155625 [PubMed - indexed for MEDLINE]
PMCID: PMC1168020
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Cited by 14 PubMed Central articles
Patient Drug Information
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Warfarin (Coumadin® )
Warfarin is used to prevent blood clots from forming or growing larger in your blood and blood vessels. It is prescribed for people with certain types of irregular heartbeat, people with prosthetic (replacement or mechan...
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Phytonadione (Mephyton® )
Phytonadione (vitamin K) is used to prevent bleeding in people with blood clotting problems or too little vitamin K in the body. Phytonadione is in a class of medications called vitamins. It works by providing vitamin K ...