In enzymology, a vitamin-K-epoxide reductase (warfarin-sensitive) () is an enzyme that catalyzes the chemical reaction 2-methyl-3-phytyl-1,4-naphthoquinone + oxidized dithiothreitol 2,3-epoxy-2,3-dihydro-2-methyl-3-phytyl-1,4-naphthoquinone + 1,4-dithiothreitol Thus, the two substrates of this enzyme are 2-methyl-3-phytyl-1,4-naphthoquinone and oxidized dithiothreitol, whereas its two products are 2,3-epoxy-2,3-dihydro-2-methyl-3-phytyl-1,4-naphthoquinone and 1,4-dithiothreitol. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH or CH2 groups of donor with a disulfide as acceptor. The systematic name of this enzyme class is 2-methyl-3-phytyl-1,4-naphthoquinone:oxidized-dithiothreitol oxidoreductase. This enzyme participates in biosynthesis of steroids. At least one compound, Warfarin is known to inhibit this enzyme. References EC 1.17.4 Enzymes of unknown structure