A new fungal peroxidase with alkaline-tolerant, chloride-enhancing activity and dye decolorization capacity

A new fungal peroxidase (Pspd) from Perenniporia subacida was purified by ammonium sulfate precipitation, DEAE-cellulose DE52 anionic exchange and Sepharose GL-6B chromatography, resulting in a high specific activity of 9.138 U mg(-1), 3.622-fold higher than that of crude enzyme at the same level. Polyacrylamide gel electrophoresis and UV-vis adsorption spectrum analysis showed that the purified enzyme is a heme-containing monomer with a molecular mass of 43.0 kDa. Optimal peroxidase activity was obtained at pH 5.5 and 30 degrees C when using 100.0 mM n-propanol as substrate, and under these conditions, the catalytic efficiency (k(cat)/K-m) is 1.57 s(-1) mu M-1. Pspd was inhibited by L-cysteine, dithiothreitol, EDTA and sodium azide, but stimulated by Mn2+, Na+, Mg2+ and K+. The enzyme is stable over a broad pH range of 7.0-8.5 after incubation for 72 h, which indicated that the enzyme is lasting alkaline-tolerant. It was worth noting that the chloride at relatively low concentrations can enhance the peroxidase activity, with concomitant increase in substrate affinity. Additionally, Pspd performed high decolorization capability toward structurally various dyes and the capability was independent of the oxidizing mediators, with 75.31% of Neutral Red (50.0 mg L-1) being decolorized by 1.5 U mL(-1) pure enzyme after incubation for 72 h. These properties demonstrated that Pspd has potentials for textile dyes decolorization applications. (C) 2012 Elsevier B.V. All rights reserved.