Synthesis of vitamin K1 2,3-epoxide in rat liver mitochondria

Metabolism of vitamin K1 in rat liver mitochondria has been studied with succinate as the source of reducing equivalents. A metabolite was isolated that comigrated with vitamin K1 epoxide using four different chromatographic systems. The purified metabolite had an ultraviolet spectrum (200-330 nm) that was identical to that of synthetic vitamin K1 epoxide. The mass spectrum of the purified metabolite was identical to that of synthetic vitamin K1 epoxide. A comparison of production of vitamin K1 epoxide by mitochondrial and microsomal preparations indicates that the mitochondrial production of vitamin K1 epoxide was about 50% of that of the microsomes. Since the mitochondrial preparation was found to have only 3.4% of the glucose-6-phosphatase activity of the microsomal preparation, it can be concluded that the vitamin K1 epoxide isolated from the mitochondrial incubations was due primarily to mitochondrial synthesis. Epoxidation of vitamin K1 in mitochondria suggests that mitochondria might be sites for vitamin K-dependent carboxylation of protein(s).