Lignin peroxidase-negative mutant of the white-rot basidiomycete Phanerochaete chrysosporium

Abstract

Phanerochaete chrysosporium produces two classes of extracellular heme proteins, designated lignin peroxidases and manganese peroxidases, that play a key role in lignin degradation. In this study we isolated and characterized a lignin peroxidase-negative mutant (lip mutant) that showed 16% of the ligninolytic activity (14C-labeled synthetic lignin -* '4CO2) exhibited by the wild type. The lip mutant did not produce detectable levels of lignin peroxidase, whereas the wild type, under identical conditions, produced 96 U of lignin peroxidase per liter. Both the wild type and the mutant produced comparable levels of manganese peroxidase and glucose oxidase, a key H202-generating secondary metabolic enzyme in P. chrysosporium. Fast protein liquid chromatographic analysis of the concentrated extracellular fluid of the lip mutant confirmed that it produced only heme proteins with manganese peroxidase activity but no detectable lignin peroxidase activity, whereas both lignin peroxidase and manganese peroxidase activities were produced by the wild type. The lip mutant appears to be a regulatory mutant that is defective in the production of all the lignin peroxidases.Phanerochaete chrysosporium, a white-rot basidiomycete, has been extensively studied as a model for fungal lignin degradation (25). Two classes of extracellular heme protein peroxidases, designated lignin peroxidases and manganese peroxidases, and an H202-generating system have been identified to date as the major components of the lignin-degrading enzyme system of this organism (25). Lignin peroxidases are glycosylated heme proteins that catalyze H202-dependent oxidation of a variety of phenolic and nonphenolic lignin model compounds, and that catalyze the oxidative cleavage of P-0-4 linkages (the most abundant linkage in lignin polymers), Cot-Co linkages, and other linkages in lignin and lignin substructure model compounds (25). The number of lignin peroxidase isozymes produced by P. chrysosporium is reported to vary from 2 to 15, based on the strain, culture conditions, and separation efficiency (24,30,41). All the lignin peroxidase isozymes oxidize veratryl alcohol to veratraldehyde but exhibit considerable differences in specific activities (9, 24). Manganese peroxidases constitute a second group of extracellular heme proteins that catalyze the H202-dependent oxidation of Mn(II) to Mn(III), which, in turn, oxidizes various phenolic substrates (25,44). Also, the manganese peroxidases have been reported to show properties of both an oxidase and a peroxidase (32). Both lignin peroxidases and manganese peroxidases require H202 for activity (15,40). Several enzymes, including glucose oxidase and glyoxal oxidase, have been reported to contribute to H202 production in lignin-degrading cultures of P. chrysosporium (8,21,22,23,25). Both lignin peroxidases and manganese peroxidases and H202-generating enzymes are produced during secondary metabolism, in response to nitrogen starvation, whereas cultures grown under nitrogenrich conditions produce no detectable pero...

cAMP-mediated differential regulation of lignin peroxidase and manganese-dependent peroxidase production in the white-rot basidiomycete Phanerochaete chrysosporium.

“…At high intracellular cAMP concentrations, both LIPs and MNPs are produced; at intermediate cAMP concentrations, only MNPs are produced; and at low concentrations, neither LIPs nor MNPs are produced. These results on differential regulation of LIP and MNP production by cAMP are consistent with our earlier results (21), which showed that an apparent regulatory mutant of P. chrysosporium, designated lip mutant, lacks the ability to produce the LIP isozymes but produces a normal complement of MNP isozymes, indicating that LIP production and MNP production are regulated differently. Similar differential regulation of LIPs and MNPs by manganese concentration in the growth medium has been observed (22,23) and the manganese requirement for transcription of the MNP gene has also been reported (24,25).…”

Degradation of 2,7-dichlorodibenzo-p-dioxin by the lignin-degrading basidiomycete Phanerochaete chrysosporium

“…Under ligninolytic conditions, P. chrysosponum secretes two heme peroxidases (LiP and MnP) in addition to an H202-generating system (18,32). These two peroxidases appear to be primarily responsible for the oxidative depolymerization of this heterogeneous, random phenylpropanoid polymer (4,18,23,27,32,54). Other studies have demonstrated that P. chrysosponium is capable of mineralizing many persistent environmental pollutants (5,6,10,21,28,35,49), including, to a limited extent, TCDD (6).…”

Degradation of polycyclic aromatic hydrocarbons by newly isolated Curvularia sp. F18, Lentinus sp. S5, and Phanerochaete sp. T20

“…Screening for potential fungi using chromogenic substances 0.1% Guaiacol, 0.1% azureB, and 0.0025% phenol red were used for the screening of potential fungi that could produce peroxidase and laccase enzymes [30][31][32][33] . Three 7-mm agar plugs containing fungal mycelia from 7-day-old cultures on MEA plates were placed on an MM plate that contained each chromogenic substance.…”

“…However, eight isolates (14.5%) were able to change at least one of the three chromogenic substances. Among the latter, three isolates consisting of F18, S5, and T20 gave the widest zone of colour changes and, therefore, were selected for further characterization because the colour changes of these substances have been reported to be related to the production of peroxidase and laccase enzymes, which are responsible for the degradation of PAHs [30][31][32][33] .…”