Abstract
Studies have been made on the properties of highly purified vitamin K_3 reductase from sweet potato. The solution of the enzyme shows a characteristic flavoprotein spectrum with maxima at 275,375 and 445mμ. The molecular weight calculated from its flavin content is about 40,000 and this value is in satisfactory agreement with that from sedimentation constant (2.86S). Evidence obtained from paper chromatography and reactivation experiment indicates that the prosthetic group is FMN. Both TPNH and DPNH serve as electron donator. Naphthoquinone derivatives, p-benzoquinone, 2,6-dichlorophenol-indophenol and ferricyanide as well as vitamin K_3 serve as electron acceptor but methylene blue, brilliant cresyl blue, cytochrome c, molecular oxygen etc. do not. Data have been presented to describe pH optima, stability, inhibitors and photooxidation of the enzyme. These results indicate that the enzyme is a hitherto unknown flavoprotein.
