Summary: | Background: Fungal DyP-type peroxidases have so far been described exclusively for basidiomycetes. Moreover, peroxidases from ascomycetes that oxidize Mn<sup>2+</sup> ions are yet not known. Methods: We describe here the physicochemical, biocatalytic, and molecular characterization of a DyP-type peroxidase (DyP, EC 1.11.1.19) from an ascomycetous fungus. Results: The enzyme oxidizes classic peroxidase substrates such as 2,6-DMP but also veratryl alcohol and notably Mn<sup>2+</sup> to Mn<sup>3+</sup> ions, suggesting a physiological function of this DyP in lignin modification. The K<sub>M</sub> value (49 µM) indicates that Mn<sup>2+</sup> ions bind with high affinity to the <i>Xgr</i>DyP protein but their subsequent oxidation into reactive Mn<sup>3+</sup> proceeds with moderate efficiency compared to MnPs and VPs. Mn<sup>2+</sup> oxidation was most effective at an acidic pH (between 4.0 and 5.0) and a hypothetical surface exposed an Mn<sup>2+</sup> binding site comprising three acidic amino acids (two aspartates and one glutamate) could be localized within the hypothetical <i>Xgr</i>DyP structure. The oxidation of Mn<sup>2+</sup> ions is seemingly supported by four aromatic amino acids that mediate an electron transfer from the surface to the heme center. Conclusions: Our findings shed new light on the possible involvement of DyP-type peroxidases in lignocellulose degradation, especially by fungi that lack prototypical ligninolytic class II peroxidases.
|