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J Theor Biol. 2011 Jun 21;279(1):143-9. doi: 10.1016/j.jtbi.2011.03.030. Epub 2011 Mar 29.

A hetero-dimer model for concerted action of vitamin K carboxylase and vitamin K reductase in vitamin K cycle.

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Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA.


Vitamin K carboxylase (VKC) is believed to convert vitamin K, in the vitamin K cycle, to an alkoxide-epoxide form which then reacts with CO(2) and glutamate to generate γ-carboxyglutamic acid (Gla). Subsequently, vitamin K epoxide reductase (VKOR) is thought to convert the alkoxide-epoxide to a hydroquinone form. By recycling vitamin K, the two integral-membrane proteins, VKC and VKOR, maintain vitamin K levels and sustain the blood coagulation cascade. Unfortunately, NMR or X-ray crystal structures of the two proteins have not been characterized. Thus, our understanding of the vitamin K cycle is only partial at the molecular level. In this study, based on prior biochemical experiments on VKC and VKOR, we propose a hetero-dimeric form of VKC and VKOR that may explain the efficient oxidation and reduction of vitamin K during the vitamin K cycle.

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