The partitioning behavior of menadione-induced NAD(P)H oxidase from the white rot fungus Phanerochaete chrysosporium has been studied in various poly(ethylene glycol) (PEG)-salt aqueous two-phase systems (ATPSs). The effects of the molecular weight of the PEG, system composition, and pH of the system on NAD(P)H oxidase partitioning were investigated at 25 degrees C. The best partition parameters were observed in the PEG 2000 18%-K2HPO4 13%-NaCl 0.5% (w/w, pH 7.0) system; the partition coefficient of total NAD(P)H oxidase activity (K-e) of the system was 0.232. While the recovery in the bottom phase (R-b) was 87.644%, this value was 20.350% in the top phase of the optimized system. The purification fold was found as 8.331 in the bottom phase. NAD(P)H oxidase purified from P. chrysosporium by the PEG-K2HPO4 two-phase system was determined to be a homodimer in its native state with a molecular weight of 116 kDa. (C) 2016 Elsevier B.V. All rights reserved.