Reductions catalyzed by a quinone and peroxidases from Phanerochaete chrysosporium.

A quinone produced from veratryl alcohol by lignin peroxidase from the white rot fungus Phanerochaete chrysosporium was tested for its ability to mediate reduction. The quinone (2-hydroxymethyl-5-methoxy-1,4-benzoquinone), reduced chemically or by cellobiose:quinone reductase isolated from cultures of the fungus, mediated the reduction of cytochrome c in reactions containing either Mn(III), a manganese-dependent peroxidase, Mn(II) and H2O2, or lignin peroxidase and H2O2. Formation of the semiquinone, the species responsible for reducing cytochrome c, was observed by electron spin resonance spectroscopy in these reactions. The production of the quinone was observed in the extracellular fraction of cultures grown under nutrient nitrogen-deficient conditions (2.4 mM ammonium tartrate) for over 10 days, starting on Day 2, but not under nutrient nitrogen-sufficient conditions. These results suggest that a quinone produced by lignin peroxidase can serve as a physiological mediator of reductive reactions catalyzed by the fungal peroxidases.