Isolation of a Novel NAD(P)H-Quinone Oxidoreductase from the Cyanobacterium Synechocystis PCC6803 |
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Authors: | Matsuo, Michinori Endo, Tsuyoshi Asada, Kozi |
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Affiliation: | Research Institute for Food Science, Kyoto University Uji, Kyoto, 611-0011 Japan |
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Abstract: | A novel NAD(P)H-quinone oxidoreductase (NQR) was isolated fromthe cyanobacterium Synechocystis PCC6803 by ion-exchange, affinityand gel-filtration chro-matographies. Isolated NQR was foundto be a drgA gene product that was a homodimer composed of 23-kDasub-units. It showed NAD(P)H-plastoquinone oxidoreductase activitywith Km values for NADPH and NADH of 12 and 48 µM respectively.The activity was inhibited by thiol-modifying reagents, butnot by rotenone, amobarbital, salicylhydroxamic acid, dicumarol,flavone, or diphenylene-iodonium chloride. Therefore, the Cys-147residue is probably involved in the catalytic reaction. Theamino acid sequence of the purified NQR had some homology withthose of NADH oxidase, NAD(P)H-flavin oxidoreductase, and nitroreductasebut did not contain either an adenine-bind-ing motif or a phosphate-bindingmotif, thus, it is a new type of NQR. 1Present address: Division of Applied Life Sciences, GraduateSchool of Agriculture, Kyoto University, Sakyo, Kyoto, 606-8502Japan.3Present address: Department of Biotechnology, Faculty of Engineering,Fukuyama University, 1 Gakuencho, Fukuyama, 729- 0251 Japan. |
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