Molecular Mechanism of the Chitinolytic Peroxygenase Reaction

Gregg Beckham, Bastien Bissaro, Bennett Streit, Ingvild Isaksen, Vincent Eijsink, Jennifer DuBois, Asmund Rohr

Research output: Contribution to journalArticlepeer-review

89 Scopus Citations

Abstract

Lytic polysaccharide monooxygenases (LPMOs) are a recently discovered class of monocopper enzymes broadly distributed across the tree of life. Recent reports indicate that LPMOs can use H2O2 as an oxidant and thus carry out a novel type of peroxygenase reaction involving unprecedented copper chemistry. Here, we present a combined computational and experimental analysis of the H2O2- mediated reaction mechanism. In silico studies, based on a model of the enzyme in complex with a crystalline substrate, suggest that a network of hydrogen bonds, involving both the enzyme and the substrate, brings H2O2 into a strained reactive conformation and guides a derived hydroxyl radical toward formation of a copper-oxyl intermediate. The initial cleavage of H2O2 and subsequent hydrogen atom abstraction from chitin by the copper-oxyl intermediate are the main energy barriers. Stopped-flow fluorimetry experiments demonstrated that the priming reduction of LPMO-Cu(II) to LPMO- Cu(I) is a fast process compared to the reoxidation reactions. Using conditions resulting in single oxidative events, we found that reoxidation of LPMO-Cu(I) is 2,000-fold faster with H2O2 than with O2, the latter being several orders of magnitude slower than rates reported for other monooxygenases. The presence of substrate accelerated reoxidation by H2O2, whereas reoxidation by O2 became slower, supporting the peroxygenase paradigm. These insights into the peroxygenase nature of LPMOs will aid in the development and application of enzymatic and synthetic copper catalysts and contribute to a further understanding of the roles of LPMOs in nature, varying from biomass conversion to chitinolytic pathogenesisdefense mechanisms.

Original languageAmerican English
Pages (from-to)1504-1513
Number of pages10
JournalProceedings of the National Academy of Sciences of the United States of America
Volume117
Issue number3
DOIs
StatePublished - 21 Jan 2020

Bibliographical note

Publisher Copyright:
© 2020 National Academy of Sciences. All rights reserved.

NREL Publication Number

  • NREL/JA-2A00-75859

Keywords

  • Biomass
  • Chitin
  • LPMO
  • Peroxygenase
  • QM/MM

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