Mn2+ is dispensable for the production of active MnP2 by Pleurotus ostreatus

The regulation mechanism for expression of versatile peroxidase MnP2 by the basidiomycete fungus Pleurotus ostreatus was examined using chemically defined synthetic media. Expression of MnP2 was down-regulated at the transcription level by nutrient nitrogen, e.g., NH4+, arginine or urea. As is often the case with other fungal manganese peroxidases, active MnP2 was not detected when Mn2+ was omitted from the culture, while mnp2 transcription was barely affected by Mn2+. However, Mn2+ can be substituted by an MnP2 substrate, Poly R-478, since active MnP2 was detected extracellularly when the compound was added to the culture without Mn2+. Enzyme stability assays with the purified MnP2 indicated an indispensable requirement for a substrate that can be used to complete the catalytic cycle, and avoid inactivation resulting from an excess H2O2. This report is the first of the Mn2+-independent production of an active versatile peroxidase by P. ostreatus.