PROPERTIES OF A TRANSPLASMA MEMBRANE REDOX SYSTEM OF PHANEROCHAETE-CHRYSOSPORIUM

A transplasma membrane redox system of Phanerochaete chrysosporium was studied using ferricyanide, a membrane-impermeable electron acceptor. Rates of reduction were dependent upon initial ferricyanide concentra tion and mycelial mass. Specific activities of 12 +/- 2 nmol/min/mg my celia (dry wt) were consistently obtained using nutrient-sufficient my celia at pH 8.0 and 10 mM ferricyanide. Upon nutrient limitation (eith er carbon or nitrogen), activity decreased. Reduction was inhibited by carbonyl cyanide m-chloromethoxyphenyl hydrazone, 2,4-dinitrophenol, and sodium azide but not by potassium cyanide at 100 nmol/mg mg myceli a, Ferricyanide reduction and proton export rates increased with pH ab ove the physiological pH for the fungus. The stimulation in proton exp orted by the addition of ferricyanide was equal to the rate of ferricy anide reduced at pH 8.0 when Hepes buffer was used. The relevance of t hese findings with regard to the physiological pH optimum of the fungu s and the metabolism of pollutants by this fungus is discussed. (C) 19 95 Academic Press, Inc.