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Title: Fungal lignin peroxidase does not produce the veratryl alcohol cation radical as a diffusible ligninolytic oxidant

Abstract

Peroxidases are considered essential agents of lignin degradation by white-rot basidiomycetes. However, low-molecular-weight oxidants likely have a primary role in lignin breakdown because many of these fungi delignify wood before its porosity has sufficiently increased for enzymes to infiltrate. It has been proposed that lignin peroxidases (LiPs, EC 1.11.1.14) fulfill this role by oxidizing the secreted fungal metabolite veratryl alcohol (VA) to its aryl cation radical (VA+•), releasing it to act as a one-electron lignin oxidant within woody plant cell walls. Here, we attached the fluorescent oxidant sensor BODIPY 581/591 throughout beads with a nominal porosity of 6 kDa and assessed whether peroxidase-generated aryl cation radical systems could oxidize the beads. As positive control, we used the 1,2,4,5-tetramethoxybenzene (TMB) cation radical, generated from TMB by horseradish peroxidase. This control oxidized the beads to depths that increased with the amount of oxidant supplied, ultimately resulting in completely oxidized beads. A reaction–diffusion computer model yielded oxidation profiles that were within the 95% confidence intervals for the data. By contrast, bead oxidation caused by VA and the LiPA isozyme of Phanerochaete chrysosporium was confined to a shallow shell of LiP-accessible volume at the bead surface, regardless of how much oxidant was supplied. Thismore » finding contrasted with the modeling results, which showed that if the LiP/VA system were to release VA+•, it would oxidize the bead interiors. We conclude that LiPA releases insignificant quantities of VA+• and that a different mechanism produces small ligninolytic oxidants during white rot.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1540309
Grant/Contract Number:  
SC0006929
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Biological Chemistry
Additional Journal Information:
Journal Volume: 293; Journal Issue: 13; Journal ID: ISSN 0021-9258
Publisher:
American Society for Biochemistry and Molecular Biology
Country of Publication:
United States
Language:
English
Subject:
Biochemistry & Molecular Biology

Citation Formats

Houtman, Carl J., Maligaspe, Eranda, Hunt, Christopher G., Fernández-Fueyo, Elena, Martínez, Angel T., and Hammel, Kenneth E. Fungal lignin peroxidase does not produce the veratryl alcohol cation radical as a diffusible ligninolytic oxidant. United States: N. p., 2018. Web. doi:10.1074/jbc.ra117.001153.
Houtman, Carl J., Maligaspe, Eranda, Hunt, Christopher G., Fernández-Fueyo, Elena, Martínez, Angel T., & Hammel, Kenneth E. Fungal lignin peroxidase does not produce the veratryl alcohol cation radical as a diffusible ligninolytic oxidant. United States. doi:10.1074/jbc.ra117.001153.
Houtman, Carl J., Maligaspe, Eranda, Hunt, Christopher G., Fernández-Fueyo, Elena, Martínez, Angel T., and Hammel, Kenneth E. Fri . "Fungal lignin peroxidase does not produce the veratryl alcohol cation radical as a diffusible ligninolytic oxidant". United States. doi:10.1074/jbc.ra117.001153. https://www.osti.gov/servlets/purl/1540309.
@article{osti_1540309,
title = {Fungal lignin peroxidase does not produce the veratryl alcohol cation radical as a diffusible ligninolytic oxidant},
author = {Houtman, Carl J. and Maligaspe, Eranda and Hunt, Christopher G. and Fernández-Fueyo, Elena and Martínez, Angel T. and Hammel, Kenneth E.},
abstractNote = {Peroxidases are considered essential agents of lignin degradation by white-rot basidiomycetes. However, low-molecular-weight oxidants likely have a primary role in lignin breakdown because many of these fungi delignify wood before its porosity has sufficiently increased for enzymes to infiltrate. It has been proposed that lignin peroxidases (LiPs, EC 1.11.1.14) fulfill this role by oxidizing the secreted fungal metabolite veratryl alcohol (VA) to its aryl cation radical (VA+•), releasing it to act as a one-electron lignin oxidant within woody plant cell walls. Here, we attached the fluorescent oxidant sensor BODIPY 581/591 throughout beads with a nominal porosity of 6 kDa and assessed whether peroxidase-generated aryl cation radical systems could oxidize the beads. As positive control, we used the 1,2,4,5-tetramethoxybenzene (TMB) cation radical, generated from TMB by horseradish peroxidase. This control oxidized the beads to depths that increased with the amount of oxidant supplied, ultimately resulting in completely oxidized beads. A reaction–diffusion computer model yielded oxidation profiles that were within the 95% confidence intervals for the data. By contrast, bead oxidation caused by VA and the LiPA isozyme of Phanerochaete chrysosporium was confined to a shallow shell of LiP-accessible volume at the bead surface, regardless of how much oxidant was supplied. This finding contrasted with the modeling results, which showed that if the LiP/VA system were to release VA+•, it would oxidize the bead interiors. We conclude that LiPA releases insignificant quantities of VA+• and that a different mechanism produces small ligninolytic oxidants during white rot.},
doi = {10.1074/jbc.ra117.001153},
journal = {Journal of Biological Chemistry},
issn = {0021-9258},
number = 13,
volume = 293,
place = {United States},
year = {2018},
month = {2}
}

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Works referenced in this record:

Comparative genomics of Ceriporiopsis subvermispora and Phanerochaete chrysosporium provide insight into selective ligninolysis
journal, March 2012

  • Fernandez-Fueyo, E.; Ruiz-Duenas, F. J.; Ferreira, P.
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Comparison of ligninase-I and peroxidase-M2 from the white-rot fungus Phanerochaete chrysosporium
journal, February 1986

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