IUBMB Enzyme Nomenclature


Accepted name: ribosyldihydronicotinamide dehydrogenase (quinone)

Reaction: 1-(β-D-ribofuranosyl)-1,4-dihydronicotinamide + a quinone = 1-(β-D-ribofuranosyl)nicotinamide + a quinol

For diagram of reaction click here.

Other name(s): NRH:quinone oxidoreductase 2; NQO2; NAD(P)H:quinone oxidoreductase-2 (misleading); QR2; quinone reductase 2; N-ribosyldihydronicotinamide dehydrogenase (quinone); NAD(P)H:quinone oxidoreductase2 (misleading)

Systematic name: 1-(β-D-ribofuranosyl)-1,4-dihydronicotinamide:quinone oxidoreductase

Comments: A flavoprotein. Unlike EC, NAD(P)H dehydrogenase (quinone), this quinone reductase cannot use NADH or NADPH; instead it uses N-ribosyl- and N-alkyldihydronicotinamides. Polycyclic aromatic hydrocarbons, such as benz[a]anthracene, and the estrogens 17β-estradiol and diethylstilbestrol are potent inhibitors, but dicoumarol is only a very weak inhibitor [2]. This enzyme can catalyse both 2-electron and 4-electron reductions, but one-electron acceptors, such as potassium ferricyanide, cannot be reduced [3].

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Liao, S., Dulaney, J.T. and Williams-Ashman, H.G. Purification and properties of a flavoprotein catalyzing the oxidation of reduced ribosyl nicotinamide. J. Biol. Chem. 237 (1962) 2981-2987. [PMID: 14465018]

2. Zhao, Q., Yang, X.L., Holtzclaw, W.D. and Talalay, P. Unexpected genetic and structural relationships of a long-forgotten flavoenzyme to NAD(P)H:quinone reductase (DT-diaphorase). Proc. Natl. Acad. Sci. USA 94 (1997) 1669-1674. [PMID: 9050836]

3. Wu, K., Knox, R., Sun, X.Z., Joseph, P., Jaiswal, A.K., Zhang, D., Deng, P.S. and Chen, S. Catalytic properties of NAD(P)H:quinone oxidoreductase-2 (NQO2), a dihydronicotinamide riboside dependent oxidoreductase. Arch. Biochem. Biophys. 347 (1997) 221-228. [PMID: 9367528]

4. Jaiswal, A.K. Human NAD(P)H:quinone oxidoreductase2. Gene structure, activity, and tissue-specific expression. J. Biol. Chem. 269 (1994) 14502-14508. [PMID: 8182056]

[EC created 2005 as EC, transferred 2015 to EC]

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