Laccase Induced Lignin Radical Formation Kinetics Evaluated by Electron Paramagnetic Resonance Spectroscopy

Valentina Perna, Jane W. Agger, Mogens L. Andersen, Jesper Holck, Anne S. Meyer*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Laccases (EC 1.10.3.2) catalyze oxidation of phenoxyl groups in lignin during reduction of O2, and the first product is a lignin radical. The determination of laccase kinetics on lignin requires cautious interpretation due to the radical reactions involved. In this study the radicals produced during laccase catalyzed oxidation of organosolv lignin were measured by electron paramagnetic resonance (EPR) spectroscopy and used to assess the enzyme kinetics of three different fungal laccases on the lignin. The laccases originated from Trametes versicolor (T. versicolor), Ganoderma lucidum (G. lucidum), and Myceliophthora thermophila (M. thermophila), respectively. The enzymes had different affinities for the organosolv lignin substrate, and the kinetic parameters of the three laccases differed. The T. versicolor enzyme was the fastest relative to the activity of the three enzymes on the assay substrate syringaldazine, but the G. lucidum and the T. versicolor laccases had similar apparent catalytic efficiencies on the lignin substrate. The enzyme kinetic parameters must be denoted as apparent because the measured levels of radicals formed is the net sum of laccase driven formation of radicals and spontaneous radical decay reactions occurring simultaneously. Spontaneous quenching of radicals after laccase inactivation was quantitifed by EPR spectroscopy, and the initial radical decay rates were confirmed to be laccase independent. The findings expand our understanding of laccase attack on lignin in nature and are of significance in relation to use of laccase in lignocellulose and lignin biorefining.

Original languageEnglish
JournalACS Sustainable Chemistry and Engineering
Volume7
Issue number12
Pages (from-to)10425-10434
Number of pages10
ISSN2168-0485
DOIs
Publication statusPublished - 2019

Keywords

  • EPR
  • Laccase
  • Lignin
  • Michaelis-Menten kinetic
  • Radical

Cite this

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title = "Laccase Induced Lignin Radical Formation Kinetics Evaluated by Electron Paramagnetic Resonance Spectroscopy",
abstract = "Laccases (EC 1.10.3.2) catalyze oxidation of phenoxyl groups in lignin during reduction of O2, and the first product is a lignin radical. The determination of laccase kinetics on lignin requires cautious interpretation due to the radical reactions involved. In this study the radicals produced during laccase catalyzed oxidation of organosolv lignin were measured by electron paramagnetic resonance (EPR) spectroscopy and used to assess the enzyme kinetics of three different fungal laccases on the lignin. The laccases originated from Trametes versicolor (T. versicolor), Ganoderma lucidum (G. lucidum), and Myceliophthora thermophila (M. thermophila), respectively. The enzymes had different affinities for the organosolv lignin substrate, and the kinetic parameters of the three laccases differed. The T. versicolor enzyme was the fastest relative to the activity of the three enzymes on the assay substrate syringaldazine, but the G. lucidum and the T. versicolor laccases had similar apparent catalytic efficiencies on the lignin substrate. The enzyme kinetic parameters must be denoted as apparent because the measured levels of radicals formed is the net sum of laccase driven formation of radicals and spontaneous radical decay reactions occurring simultaneously. Spontaneous quenching of radicals after laccase inactivation was quantitifed by EPR spectroscopy, and the initial radical decay rates were confirmed to be laccase independent. The findings expand our understanding of laccase attack on lignin in nature and are of significance in relation to use of laccase in lignocellulose and lignin biorefining.",
keywords = "EPR, Laccase, Lignin, Michaelis-Menten kinetic, Radical",
author = "Valentina Perna and Agger, {Jane W.} and Andersen, {Mogens L.} and Jesper Holck and Meyer, {Anne S.}",
year = "2019",
doi = "10.1021/acssuschemeng.9b00723",
language = "English",
volume = "7",
pages = "10425--10434",
journal = "A C S Sustainable Chemistry & Engineering",
issn = "2168-0485",
publisher = "American Chemical Society",
number = "12",

}

Laccase Induced Lignin Radical Formation Kinetics Evaluated by Electron Paramagnetic Resonance Spectroscopy. / Perna, Valentina; Agger, Jane W.; Andersen, Mogens L.; Holck, Jesper; Meyer, Anne S.

In: ACS Sustainable Chemistry and Engineering, Vol. 7, No. 12, 2019, p. 10425-10434.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Laccase Induced Lignin Radical Formation Kinetics Evaluated by Electron Paramagnetic Resonance Spectroscopy

AU - Perna, Valentina

AU - Agger, Jane W.

AU - Andersen, Mogens L.

AU - Holck, Jesper

AU - Meyer, Anne S.

PY - 2019

Y1 - 2019

N2 - Laccases (EC 1.10.3.2) catalyze oxidation of phenoxyl groups in lignin during reduction of O2, and the first product is a lignin radical. The determination of laccase kinetics on lignin requires cautious interpretation due to the radical reactions involved. In this study the radicals produced during laccase catalyzed oxidation of organosolv lignin were measured by electron paramagnetic resonance (EPR) spectroscopy and used to assess the enzyme kinetics of three different fungal laccases on the lignin. The laccases originated from Trametes versicolor (T. versicolor), Ganoderma lucidum (G. lucidum), and Myceliophthora thermophila (M. thermophila), respectively. The enzymes had different affinities for the organosolv lignin substrate, and the kinetic parameters of the three laccases differed. The T. versicolor enzyme was the fastest relative to the activity of the three enzymes on the assay substrate syringaldazine, but the G. lucidum and the T. versicolor laccases had similar apparent catalytic efficiencies on the lignin substrate. The enzyme kinetic parameters must be denoted as apparent because the measured levels of radicals formed is the net sum of laccase driven formation of radicals and spontaneous radical decay reactions occurring simultaneously. Spontaneous quenching of radicals after laccase inactivation was quantitifed by EPR spectroscopy, and the initial radical decay rates were confirmed to be laccase independent. The findings expand our understanding of laccase attack on lignin in nature and are of significance in relation to use of laccase in lignocellulose and lignin biorefining.

AB - Laccases (EC 1.10.3.2) catalyze oxidation of phenoxyl groups in lignin during reduction of O2, and the first product is a lignin radical. The determination of laccase kinetics on lignin requires cautious interpretation due to the radical reactions involved. In this study the radicals produced during laccase catalyzed oxidation of organosolv lignin were measured by electron paramagnetic resonance (EPR) spectroscopy and used to assess the enzyme kinetics of three different fungal laccases on the lignin. The laccases originated from Trametes versicolor (T. versicolor), Ganoderma lucidum (G. lucidum), and Myceliophthora thermophila (M. thermophila), respectively. The enzymes had different affinities for the organosolv lignin substrate, and the kinetic parameters of the three laccases differed. The T. versicolor enzyme was the fastest relative to the activity of the three enzymes on the assay substrate syringaldazine, but the G. lucidum and the T. versicolor laccases had similar apparent catalytic efficiencies on the lignin substrate. The enzyme kinetic parameters must be denoted as apparent because the measured levels of radicals formed is the net sum of laccase driven formation of radicals and spontaneous radical decay reactions occurring simultaneously. Spontaneous quenching of radicals after laccase inactivation was quantitifed by EPR spectroscopy, and the initial radical decay rates were confirmed to be laccase independent. The findings expand our understanding of laccase attack on lignin in nature and are of significance in relation to use of laccase in lignocellulose and lignin biorefining.

KW - EPR

KW - Laccase

KW - Lignin

KW - Michaelis-Menten kinetic

KW - Radical

U2 - 10.1021/acssuschemeng.9b00723

DO - 10.1021/acssuschemeng.9b00723

M3 - Journal article

VL - 7

SP - 10425

EP - 10434

JO - A C S Sustainable Chemistry & Engineering

JF - A C S Sustainable Chemistry & Engineering

SN - 2168-0485

IS - 12

ER -