Comprehensive investigation of a dye-decolorizing peroxidase and a manganese peroxidase from Irpex lacteus F17, a lignin-degrading basidiomycete

Zihong Duan,Binjie Liu,Rong Jia,Rui Shen,Mengwei Yao

doi:10.1186/s13568-018-0648-6

Abstract

Irpex lacteus F17 is well-known for its ability to degrade recalcitrant aromatic pollutants, which mainly results from the action of the manganese peroxidase (MnP) that it is able to produce. Recently, the genome sequencing and annotation of this strain provided comprehensive picture of the ligninolytic peroxidase gene family. In addition to revealing the presence of 13 MnPs, genes for five dye-decolorizing peroxidases (DyPs) were also discovered in the I. lacteus F17 genome, which are unrelated to the fungal class II peroxidases. In the present study, amino acid sequences of five DyPs and 13 MnPs, representing two different families of heme peroxidases, were analyzed. Of these, two enzymes, a DyP (Il-DyP4) and a MnP (Il-MnP6) were expressed respectively in Escherichia coli, and were characterized by comparing their molecular models, substrate specificities, and catalytic features. The results showed that Il-DyP4 possessed a higher catalytic efficiency for some representative substrates, and a stronger decolorizing ability to a wide range of synthetic dyes in acidic conditions. Based on electrochemical measurements, Il-DyP4 was found to have a high redox potential of 27 mV at pH 3.5, which was superior to that of Il-MnP6 (− 75 mV), thereby contributing to its ability to oxidize high redox potential substrates, such as veratryl alcohol and polymeric dye Poly R-478. The results highlighted the potential of Il-DyP4 for use in industrial and environmental applications.

Highlights

Lignocellulose is a structural component of the plant cell wall, mainly comprising cellulose, hemicellulose, and lignin
The results showed that the catalytic efficiency of Il-DyP4 in the reduction of hydrogen peroxide (H2O2) was an order of magnitude higher than that of Il-MnP6
The fungus can produce lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase simultaneously, which is similar to P. radiata and T. versicolor (Novotný et al 2009)

Summary

Introduction

Lignocellulose is a structural component of the plant cell wall, mainly comprising cellulose, hemicellulose, and lignin It is the largest renewable resource in nature and the most promising feedstock for the production of many valuable substances, such as biofuels, chemicals, and materials, from plant sources (Balat 2011). Wood-decaying fungi, one of several groups of lignocellulose decomposers in nature, have an important role in the terrestrial carbon cycle (Kellner et al 2014) They are common inhabitants of forest litter and fallen trees and have typically been classified as white-rot fungi and brown-rot fungi, according to their ability to biodegrade lignin. Recently published work, based on the genomic data from 33 species of fungi, suggests that a more nuanced categorization of wood decay modes between white-rot and brown-rot fungi is necessary, because numerous other classes of enzyme were found to be involved in lignin degradation in addition to PODs (Riley et al 2014). The dye-decolorizing peroxidases (DyPs), a second new heme peroxidase superfamily, were identified in fungi that have been shown to degrade model lignin compounds, and were widespread in white-rot fungi, such as Auricularia delicate and Trametes versicolor, whereas brown-rot fungi lack DyPs (Floudas et al 2012, 2015)

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Results

Conclusion