ENZYME entry: EC 1.6.5.5

Accepted Name
NADPH:quinone reductase.
Alternative Name(s)
Quinone oxidoreductase.
Zeta-crystallin.
Reaction catalysed
NADPH + 2 quinone <=> NADP(+) + 2 semiquinone
Cofactor(s)
Zn(2+).
Comment(s)
  • Specific for NADPH.
  • Catalyzes the one-electron reduction of certain quinones, with the orthoquinones 1,2-naphthoquinone and 9,10-phenanthrenequinone being the best substrates.
  • Dicoumarol (cf. EC 1.6.5.2) 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 O(2).
  • Abundant in the lens of the eye of some mammalian species.
Cross-references
PROSITEPDOC00058
BRENDA1.6.5.5
EC2PDB1.6.5.5
ExplorEnz1.6.5.5
PRIAM enzyme-specific profiles1.6.5.5
KEGG Ligand Database for Enzyme Nomenclature1.6.5.5
IUBMB Enzyme Nomenclature1.6.5.5
IntEnz1.6.5.5
MEDLINEFind literature relating to 1.6.5.5
MetaCyc1.6.5.5
UniProtKB/Swiss-Prot
P28304, QOR1_ECOLI;  P11415, QOR_CAVPO;  Q08257, QOR_HUMAN;  
Q28452, QOR_LAMGU;  P42865, QOR_LEIAM;  P47199, QOR_MOUSE;  
Q0MVN8, QOR_PIG;  Q5R4S7, QOR_PONAB;  P43903, QOR_PSEAE;  
Q6AYT0, QOR_RAT;  P40783, QOR_SALTY;  O74489, QOR_SCHPO;  
P38230, QOR_YEAST;  

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