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. 2017 Dec 13;7(4):20. doi: 10.3390/jpm7040020

Figure 1.

Figure 1

Schematic of the effect of warfarin and involvement of CYP2C9, CYP4F2, and vitamin K epoxide reductase complex subunit 1 (VKORC1) on the vitamin K cycle. VKORC1 and NAD(P)H:Quinone oxidoreductase (NQO) reduce vitamin K1 to active vitamin K1 dihydroquinone. Gamma-glutamyl carboxylase (GGCX) catalyzes carboxylation of glutamate residues activating clotting factors II, VII, IX, and X in a vitamin K1 dihydroquinone dependent manner. VKORC1 reduces vitamin K1 epoxide to vitamin K1, restarting the cycle. Warfarin impairs VKORC1 and the reduction of vitamin K1. Warfarin is metabolized by CYP2C9. Vitamin K1 can be removed from the cycle by CYP4F2 by hydroxylation.