NADPH-specific quinone reductase. Is most active with quinone derivatives and ferricyanide as electron acceptors. Can use menadione, 1,4-naphthoquinone and 1,4-benzoquinone. a quinone + H(+) + NADPH = a quinol + NADP(+) Optimum pH is 7.0. Homodimer. Induced by 2-methylene-4-butyrolactone (MBL). Overexpression leads to increased resistance to the tumoricidal agent DMP 840. Belongs to the oxidoreductase MdaB family.