Manganese peroxidases, lignin peroxidases, and versatile peroxidases secreted by white rot fungi are supposed to play an essential role in lignin degradation. Thus, these enzymes have attracted significant attention as potential biocatalysts. Versatile peroxidases are the most interesting ones, since they comprise activities of manganese and lignin peroxidases. Herein, we demonstrate how the properties of a new manganese peroxidase from Moniliophthora roreri, designated MrMnP1, were shifted towards those of a versatile peroxidase. MrMnP1 was cloned in Pichia pastoris X-33 and highly expressed in a fed-batch fermentation, yielding 132 mg L-1 of active enzyme. To extend the substrate spectrum of MrMnP1, a catalytically active tryptophan present in lignin and versatile peroxidases was first introduced. Additionally, the role of five amino acids at positions adjacent to the catalytic tryptophan was elucidated through their replacement by those found in a versatile peroxidase from Pleurotus eryngii. The resulting mutants demonstrated new activities towards high-redox-potential substrates, such as lignin dimers, veratryl alcohol, and the azo dye Reactive Black 5.
Keywords: biocatalysis; enzymes; mutagenesis; renewable resources; structure-activity relationships.
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