Quinone reductase that provides resistance to thiol-specific stress caused by electrophilic quinones (PubMed:24915188). Shows a preference for benzoquinones (PubMed:24915188). Also exhibits azoreductase activity. Catalyzes the reductive cleavage of the azo bond in aromatic azo compounds to the corresponding amines (PubMed:17904577, PubMed:20057057). NADPH is the preferred electron donor for azoreductase activity, but it can also use NADH (PubMed:17904577). Can reduce different classes of azo dyes, including the common azo dyes methyl red and p-aminoazobenzene sulfonamide (PAABSA) (PubMed:17904577, PubMed:20057057). Can activate several azo pro-drugs used in the treatment of inflammatory bowel disease (IBD), including balsalazide, sulfasalazine and olsalazine (PubMed:17904577, PubMed:20057057). Also acts as a nitrodeductase, and can reduce and hence activate the nitroaromatic drug nitrofurazone, a broad spectrum antibiotic (PubMed:22355582). 2 a quinone + H(+) + NADPH = 2 a 1,4-benzosemiquinone + NADP(+) 2 a quinone + H(+) + NADH = 2 a 1,4-benzosemiquinone + NAD(+) anthranilate + N,N-dimethyl-1,4-phenylenediamine + 2 NAD(+) = 2-(4-dimethylaminophenyl)diazenylbenzoate + 2 H(+) + 2 NADH Binds 1 FMN per subunit. Azoreductase activity increases with salt strength. kcat is 13 sec(-1) with methyl red as substrate. kcat is 13 sec(-1) with sulfasalazine as substrate. kcat is 37 sec(-1) with balsalazide as substrate. kcat is 2.5 sec(-1) with olsalazine as substrate. kcat is 10 sec(-1) with NADH as substrate. kcat is 34 sec(-1) with NADPH as substrate. Homodimer (PubMed:17904577). Homotetramer formed by a dimer of dimers when the ionic strength is high (PubMed:17904577). Rate of quinone reduction is higher than reduction of azo substrates, suggesting the enzyme is better suited for carrying out quinone rather than azo reduction. Belongs to the azoreductase type 1 family.