Functional Promoter Polymorphism in the VKORC1 Gene is no Major Genetic Determinant for Vitamin K Dependent Coagulation Factor Activity

Abstract

Vitamin K epoxide reductase (VKOR) recycles vitamin K epoxide to active hydroquinone, which is used subsequently as a co-factor in the γ-carboxylation of glutamic acid residues in blood coagulation factors. VKORC1, a subunit of the VKOR complex, has recently been shown to possess this activity (Fig. 1). A VKORC1 promoter polymorphism (c.-1639 G > A) rs 9926231 has been reported to have a substantial impact on VKORC1 mRNA expression and reduces the VKOR activity by 50 %. VKOR activity itself is the rate limiting step in γ-carboxylation of vitamin K-dependent coagulation factors II, VII, IX, X, as well as protein C, S, Z. All these proteins reach full biological activity by sufficient γ-carboxylation, requiring vitamin K hydroquinone. Therefore, γ-carboxylation is indirectly involved in the coagulation cascade and VKORC1 genotype has been hypothesized to influence individual activity of the previously mentioned factors.