Characterization of a transplasma membrane redox system of the brown rot fungus Gloeophyllum trabeum

The transplasma membrane redox system of the brown rot fungus Gloeophyllum trabeum was characterized with ferricyanide reduction kinetics. Nitrogen deficiency did not statistically affect the ferricyanide reduction rate, which depended on initial ferricyanide concentration and initial mycelial mass. The reduction rate increased with pH above pH 5.0, and was statistically lower in HEPES buffer (pH 8.0) than in potassium phosphate buffer (pH 8.0). Carbonyl cyanide m-chloromethoxyphenyl hydrazone, 2,4-dinitrophenol and sodium azide were efficient inhibitors of the transplasma membrane redox system. The quinone reducing activity of extracellular, membrane-bound, and intracellular quinone reductases of G. trabeum was tested, extracellular quinone reducing activity was not observed under the examined culture conditions. Quinone reduction by mycelium and the intracellular enzyme showed different kinetic constants. The fungus produced constitutive intracellular benzoquinone reductases, which are NAD(P)H-dependent.