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EC 1.6.5.5 Details
EC number
1.6.5.5
Accepted name
NADPH:quinone reductase
Reaction
NADPH + H+ + 2 quinone = NADP+ + 2 semiquinone
Other name(s)
NADPH2:quinone reductase
Systematic name
NADPH:quinone oxidoreductase
CAS registry number
9032-20-6
Comment
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 1.6.5.2 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.
History
created 1999
EC Tree
1.7.1.8 created 2002, deleted 2002