The Enzyme Database

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Accepted name: NADPH:quinone reductase
Reaction: NADPH + H+ + 2 quinone = NADP+ + 2 semiquinone
Other name(s): NADPH2:quinone reductase
Systematic name: NADPH:quinone oxidoreductase
Comments: A zinc enzyme, specific for NADPH. Catalyses the one-electron reduction of certain quinones, with the orthoquinones 1,2-naphthoquinone and 9,10-phenanthrenequinone being the best substrates [1]. Dicoumarol [cf. EC NAD(P)H dehydrogenase (quinone)] and nitrofurantoin are competitive inhibitors with respect to the quinone substrate. The semiquinone free-radical product may be non-enzymically reduced to the hydroquinone or oxidized back to quinone in the presence of O2 [1]. In some mammals, the enzyme is abundant in the lens of the eye, where it is identified with the protein ζ-crystallin.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9032-20-6
1.  Rao, P.V., Krishna, C.M. and Zigler, J.S., Jr. Identification and characterization of the enzymatic activity of zeta-crystallin from guinea pig lens. A novel NADPH:quinone oxidoreductase. J. Biol. Chem. 267 (1992) 96–102. [PMID: 1370456]
2.  Duhaiman, A.S. Kinetic properties of camel lens ζ-crystallin. Int. J. Biochem. Cell Biol. 28 (1996) 1163–1168. [PMID: 8930141]
3.  Bazzi, M.D. Interaction of camel lens ζ-crystallin with quinones: portrait of a substrate by fluorescence spectroscopy. Arch. Biochem. Biophys. 395 (2001) 185–190. [PMID: 11697855]
4.  Tang, A. and Curthoys, N.P. Identification of ζ-crystallin/NADPH:quinone reductase as a renal glutaminase mRNA pH response element-binding protein. J. Biol. Chem. 276 (2001) 21375–21380. [PMID: 11294877]
[EC created 1999]

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