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Vitamin K epoxide reductase (VKOR) recycles reduced vitamin K, which is used subsequently as a co-factor in the gamma-carboxylation of glutamic acid residues in blood coagulation enzymes. VKORC1, a subunit of the VKOR complex, has recently been shown to possess this activity. Here, we show that VKORC1 is a member of a large family of predicted enzymes that are present in vertebrates, Drosophila, plants, bacteria and archaea. Four cysteine residues and one residue, which is either serine or threonine, are identified as likely active-site residues. In some plant and bacterial homologues the VKORC1 homologous domain is fused with domains of the thioredoxin family of oxidoreductases. These might reduce disulfide bonds of VKORC1-like enzymes as a prerequisite for their catalytic activities.

Original publication




Journal article


Trends Biochem Sci

Publication Date





289 - 292


Amino Acid Sequence, Animals, Binding Sites, Catalysis, Humans, Mixed Function Oxygenases, Molecular Sequence Data, Oxidoreductases, Sequence Alignment, Sequence Homology, Nucleic Acid, Thioredoxins, Vitamin K, Vitamin K Epoxide Reductases