title: Purification and properties of a factor from rat liver cytosol which stimulates vitamin K epoxide reductase.
abstract: Two protein type factors which stimulate the reduction of vitamin K1-2,3-epoxide to vitamin K1 have been separated from the 105,000g-supernatant fraction (cytosol) of rat liver homogenates. One of these factors is rather labile. However the other factor was sufficiently stable to permit 900-fold purification following sequential column chromatography on DEAE-Sephacel, QAE-Sephadex, CM-Sephadex, and Sephacryl S-200. Four milligrams of this purified material were obtained in 32% yield from 11 g of soluble cytosolic protein. This factor appeared to be homogeneous as determined by gel electrophoresis and has a molecular weight of about 38,000 as determined by gel filtration. The final preparation had no vitamin K epoxide reductase activity in the presence or absence of either NADH or dithiothreitol. The results of kinetic studies using this factor were consistent with its acting as a nonessential activator of the microsome catalyzed reduction of vitamin K1-2,3-epoxide. The factor did not cause a large change in the apparent Km (2.2-2.5 microM) of vitamin K epoxide reductase, but the apparent Vmax was increased about fourfold.
mesh_terms: D000818:Animals; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D008970:Molecular Weight; D051381:Rats; D064417:Vitamin K Epoxide Reductases
chemical_list: D006899:Mixed Function Oxygenases; D064417:Vitamin K Epoxide Reductases