ID 1.6.5.5 DE NADPH:quinone reductase. AN quinone oxidoreductase. AN zeta-crystallin. CA 2 a quinone + NADPH + H(+) = 2 a 1,4-benzosemiquinone + NADP(+). CC -!- Specific for NADPH. CC -!- Catalyzes the one-electron reduction of certain quinones, with the CC orthoquinones 1,2-naphthoquinone and 9,10-phenanthrenequinone being CC the best substrates. CC -!- Dicoumarol (cf. EC 1.6.5.2) and nitrofurantoin are competitive CC inhibitors with respect to the quinone substrate. CC -!- The semiquinone free-radical product may be non-enzymically reduced CC to the hydroquinone or oxidized back to quinone in the presence of CC O2. CC -!- Abundant in the lens of the eye of some mammalian species. DR P28304, QOR1_ECOLI ; Q53FA7, QORX_HUMAN ; O97764, QOR_BOVIN ; DR P11415, QOR_CAVPO ; Q08257, QOR_HUMAN ; Q28452, QOR_LAMGU ; DR P42865, QOR_LEIAM ; P47199, QOR_MOUSE ; Q0MVN8, QOR_PIG ; DR Q5R4S7, QOR_PONAB ; P43903, QOR_PSEAE ; Q6AYT0, QOR_RAT ; DR P40783, QOR_SALTY ; O74489, QOR_SCHPO ; P38230, QOR_YEAST ; DR Q9AYU1, QR1_TRIVS ; Q9HCJ6, VAT1L_HUMAN; Q80TB8, VAT1L_MOUSE; DR Q8JFV8, VAT1_DANRE ; Q99536, VAT1_HUMAN ; Q62465, VAT1_MOUSE ; DR Q3MIE4, VAT1_RAT ; P19333, VAT1_TETCF ; //