Recent findings in understanding the biological function of vitamin K
Uotila, L.; Suttie, J.W.
Medical Biology 60(1): 16-24
1982
ISSN/ISBN: 0302-2137 PMID: 6803084 Document Number: 193213
The review notes that vitamin K is required for the posttranslational modification of liver precursors of prothrombin, blood coagulation Factors VII, IX, and X, and additional proteins of undetermined functions in plasma and other tissues. The modification involves the formation of gamma -carboxyglutamate acid, an acidic amino acid needed for the interaction of those proteins with calcium ions. The vitamin is a cofactor of a unique microsomal carboxylase which requires the reduced form of vitamin K, CO2 and molecular oxygen. The vitamin seems to be oxidized to its 2,3-epoxide during carboxylation. Liver microsomes also contain an enzyme which catalyses the reduction of the epoxide to the vitamin, vitamin K epoxide reductase, and some vitamin K reductases. The expoxide reductase seems to be the site of the anticoagulant action of 4-hydroxycoumarins, commonly used as anticoagulants given by mouth.