Category: biosynthesis
Catalytic cycle that regenerates active vitamin K hydroquinone (KH2) after each γ-carboxylation event. γ-Carboxylase uses KH2 + O2 + CO2 to add a γ-carboxyl group to glutamate residues on vitamin-K-dependent proteins (factors II, VII, IX, X + proteins C, S, Z; also osteocalcin and MGP). KH2 is oxidized to vitamin K epoxide in the reaction. VKORC1 reduces the epoxide back to vitamin K, completing the cycle. WARFARIN inhibits VKORC1 → epoxide accumulates → KH2 depletes → γ-carboxylation halts → undercarboxylated coagulation factors are functionally inactive.