Abstract

Intracellular NADH:quinone reductase involved in degradation of aromatic compounds including lignin was purified and characterized from white rot fungus Trametes versicolor. The activity of quinone reductase was maximal after 3 days of incubation in fungal culture, and the enzyme was purified to homogeneity using ion-exchange, hydrophobic interaction, and gel filtration chromatographies. The purified enzyme has a molecular mass of 41 kDa as determined by SDS-PAGE, and exhibits a broad temperature optimum between 20-40°C, with a pH optimum of 6.0. The enzyme preferred FAD as a cofactor and NADH rather than NADPH as an electron donor. Among quinone compounds tested as substrate, menadione showed the highest enzyme activity followed by 1,4-benzoquinone. The enzyme activity was inhibited by CuSO4, HgCl2, MgSO4, MnSO4, AgNO3, dicumarol, KCN, NaN3, and EDTA. Its Km and Vmax with NADH as an electron donor were 23 μM and 101 mM/mg per min, respectively, and showed a high substrate affinity. Purified quinone reductase could reduce 1,4-benzoquinone to hydroquinone, and induction of this enzyme was higher by 1,4-benzoquinone than those of other quinone compounds.

• Keywords: quinone; NADH:quinone reductase; Trametes versicolor; enzyme purification