1
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Ayuso-Fernández I, Emrich-Mills TZ, Haak J, Golten O, Hall KR, Schwaiger L, Moe TS, Stepnov AA, Ludwig R, Cutsail Iii GE, Sørlie M, Kjendseth Røhr Å, Eijsink VGH. Mutational dissection of a hole hopping route in a lytic polysaccharide monooxygenase (LPMO). Nat Commun 2024; 15:3975. [PMID: 38729930 PMCID: PMC11087555 DOI: 10.1038/s41467-024-48245-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 04/25/2024] [Indexed: 05/12/2024] Open
Abstract
Oxidoreductases have evolved tyrosine/tryptophan pathways that channel highly oxidizing holes away from the active site to avoid damage. Here we dissect such a pathway in a bacterial LPMO, member of a widespread family of C-H bond activating enzymes with outstanding industrial potential. We show that a strictly conserved tryptophan is critical for radical formation and hole transference and that holes traverse the protein to reach a tyrosine-histidine pair in the protein's surface. Real-time monitoring of radical formation reveals a clear correlation between the efficiency of hole transference and enzyme performance under oxidative stress. Residues involved in this pathway vary considerably between natural LPMOs, which could reflect adaptation to different ecological niches. Importantly, we show that enzyme activity is increased in a variant with slower radical transference, providing experimental evidence for a previously postulated trade-off between activity and redox robustness.
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Affiliation(s)
- Iván Ayuso-Fernández
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway.
| | - Tom Z Emrich-Mills
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Julia Haak
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
- Institute of Inorganic Chemistry, University of Duisburg-Essen, 45141, Essen, Germany
| | - Ole Golten
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Kelsi R Hall
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Lorenz Schwaiger
- Biocatalysis and Biosensing Laboratory, Department of Food Sciences and Technology, Institute of Food Science and Technology, University of Natural Resources and Life Sciences (BOKU), Muthgasse 18/2, Vienna, 1190, Austria
| | - Trond S Moe
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Anton A Stepnov
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Roland Ludwig
- Biocatalysis and Biosensing Laboratory, Department of Food Sciences and Technology, Institute of Food Science and Technology, University of Natural Resources and Life Sciences (BOKU), Muthgasse 18/2, Vienna, 1190, Austria
| | - George E Cutsail Iii
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
- Institute of Inorganic Chemistry, University of Duisburg-Essen, 45141, Essen, Germany
| | - Morten Sørlie
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Åsmund Kjendseth Røhr
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Vincent G H Eijsink
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway.
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2
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Hagemann MM, Wieduwilt EK, Hedegård ED. Understanding the initial events of the oxidative damage and protection mechanisms of the AA9 lytic polysaccharide monooxygenase family. Chem Sci 2024; 15:2558-2570. [PMID: 38362420 PMCID: PMC10866358 DOI: 10.1039/d3sc05933b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 12/31/2023] [Indexed: 02/17/2024] Open
Abstract
Lytic polysaccharide monooxygenase (LPMO) is a new class of oxidoreductases that boosts polysaccharide degradation employing a copper active site. This boost may facilitate the cost-efficient production of biofuels and high-value chemicals from polysaccharides such as lignocellulose. Unfortunately, self-oxidation of the active site inactivates LPMOs. Other oxidoreductases employ hole-hopping mechanisms as protection against oxidative damage, but little is generally known about the details of these mechanisms. Herein, we employ highly accurate theoretical models based on density functional theory (DFT) molecular mechanics (MM) hybrids to understand the initial steps in LPMOs' protective measures against self-oxidation; we identify several intermediates recently proposed from experiment, and quantify which are important for protective hole-hopping pathways. Investigations on two different LPMOs show consistently that a tyrosine residue close to copper is crucial for protection: this explains recent experiments, showing that LPMOs without this tyrosine are more susceptible to self-oxidation.
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Affiliation(s)
- Marlisa M Hagemann
- Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark Campusvej 55 5230 Odense Denmark
| | - Erna K Wieduwilt
- Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark Campusvej 55 5230 Odense Denmark
| | - Erik D Hedegård
- Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark Campusvej 55 5230 Odense Denmark
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3
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Munzone A, Eijsink VGH, Berrin JG, Bissaro B. Expanding the catalytic landscape of metalloenzymes with lytic polysaccharide monooxygenases. Nat Rev Chem 2024; 8:106-119. [PMID: 38200220 DOI: 10.1038/s41570-023-00565-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2023] [Indexed: 01/12/2024]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) have an essential role in global carbon cycle, industrial biomass processing and microbial pathogenicity by catalysing the oxidative cleavage of recalcitrant polysaccharides. Despite initially being considered monooxygenases, experimental and theoretical studies show that LPMOs are essentially peroxygenases, using a single copper ion and H2O2 for C-H bond oxygenation. Here, we examine LPMO catalysis, emphasizing key studies that have shaped our comprehension of their function, and address side and competing reactions that have partially obscured our understanding. Then, we compare this novel copper-peroxygenase reaction with reactions catalysed by haem iron enzymes, highlighting the different chemistries at play. We conclude by addressing some open questions surrounding LPMO catalysis, including the importance of peroxygenase and monooxygenase reactions in biological contexts, how LPMOs modulate copper site reactivity and potential protective mechanisms against oxidative damage.
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Affiliation(s)
- Alessia Munzone
- UMR1163 Biodiversité et Biotechnologie Fongiques, INRAE, Aix Marseille University, Marseille, France
| | - Vincent G H Eijsink
- Faculty of Chemistry, Biotechnology, and Food Science, The Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Jean-Guy Berrin
- UMR1163 Biodiversité et Biotechnologie Fongiques, INRAE, Aix Marseille University, Marseille, France
| | - Bastien Bissaro
- UMR1163 Biodiversité et Biotechnologie Fongiques, INRAE, Aix Marseille University, Marseille, France.
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4
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Zhao J, Zhuo Y, Diaz DE, Shanmugam M, Telfer AJ, Lindley PJ, Kracher D, Hayashi T, Seibt LS, Hardy FJ, Manners O, Hedison TM, Hollywood KA, Spiess R, Cain KM, Diaz-Moreno S, Scrutton NS, Tovborg M, Walton PH, Heyes DJ, Green AP. Mapping the Initial Stages of a Protective Pathway that Enhances Catalytic Turnover by a Lytic Polysaccharide Monooxygenase. J Am Chem Soc 2023; 145:20672-20682. [PMID: 37688545 PMCID: PMC10515631 DOI: 10.1021/jacs.3c06607] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Indexed: 09/11/2023]
Abstract
Oxygenase and peroxygenase enzymes generate intermediates at their active sites which bring about the controlled functionalization of inert C-H bonds in substrates, such as in the enzymatic conversion of methane to methanol. To be viable catalysts, however, these enzymes must also prevent oxidative damage to essential active site residues, which can occur during both coupled and uncoupled turnover. Herein, we use a combination of stopped-flow spectroscopy, targeted mutagenesis, TD-DFT calculations, high-energy resolution fluorescence detection X-ray absorption spectroscopy, and electron paramagnetic resonance spectroscopy to study two transient intermediates that together form a protective pathway built into the active sites of copper-dependent lytic polysaccharide monooxygenases (LPMOs). First, a transient high-valent species is generated at the copper histidine brace active site following treatment of the LPMO with either hydrogen peroxide or peroxyacids in the absence of substrate. This intermediate, which we propose to be a CuII-(histidyl radical), then reacts with a nearby tyrosine residue in an intersystem-crossing reaction to give a ferromagnetically coupled (S = 1) CuII-tyrosyl radical pair, thereby restoring the histidine brace active site to its resting state and allowing it to re-enter the catalytic cycle through reduction. This process gives the enzyme the capacity to minimize damage to the active site histidine residues "on the fly" to increase the total turnover number prior to enzyme deactivation, highlighting how oxidative enzymes are evolved to protect themselves from deleterious side reactions during uncoupled turnover.
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Affiliation(s)
- Jingming Zhao
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Ying Zhuo
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Daniel E. Diaz
- Department
of Chemistry, University of York, Heslington, York YO10 5DD, U.K.
| | - Muralidharan Shanmugam
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Abbey J. Telfer
- Department
of Chemistry, University of York, Heslington, York YO10 5DD, U.K.
- Harwell
Science and Innovation Campus, Diamond Light
Source Ltd., Didcot, Oxfordshire OX11 0DE, U.K.
| | - Peter J. Lindley
- Department
of Chemistry, University of York, Heslington, York YO10 5DD, U.K.
| | - Daniel Kracher
- Institute
of Molecular Biotechnology, Graz University
of Technology, Petersgasse
14, Graz 8010, Austria
| | - Takahiro Hayashi
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Lisa S. Seibt
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Florence J. Hardy
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Oliver Manners
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Tobias M. Hedison
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Katherine A. Hollywood
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Reynard Spiess
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Kathleen M. Cain
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Sofia Diaz-Moreno
- Harwell
Science and Innovation Campus, Diamond Light
Source Ltd., Didcot, Oxfordshire OX11 0DE, U.K.
| | - Nigel S. Scrutton
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | | | - Paul H. Walton
- Department
of Chemistry, University of York, Heslington, York YO10 5DD, U.K.
| | - Derren J. Heyes
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Anthony P. Green
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
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5
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Hall K, Joseph C, Ayuso-Fernández I, Tamhankar A, Rieder L, Skaali R, Golten O, Neese F, Røhr ÅK, Jannuzzi SAV, DeBeer S, Eijsink VGH, Sørlie M. A Conserved Second Sphere Residue Tunes Copper Site Reactivity in Lytic Polysaccharide Monooxygenases. J Am Chem Soc 2023; 145:18888-18903. [PMID: 37584157 PMCID: PMC10472438 DOI: 10.1021/jacs.3c05342] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Indexed: 08/17/2023]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are powerful monocopper enzymes that can activate strong C-H bonds through a mechanism that remains largely unknown. Herein, we investigated the role of a conserved glutamine/glutamate in the second coordination sphere. Mutation of the Gln in NcAA9C to Glu, Asp, or Asn showed that the nature and distance of the headgroup to the copper fine-tune LPMO functionality and copper reactivity. The presence of Glu or Asp close to the copper lowered the reduction potential and decreased the ratio between the reduction and reoxidation rates by up to 500-fold. All mutants showed increased enzyme inactivation, likely due to changes in the confinement of radical intermediates, and displayed changes in a protective hole-hopping pathway. Electron paramagnetic resonance (EPR) and X-ray absorption spectroscopic (XAS) studies gave virtually identical results for all NcAA9C variants, showing that the mutations do not directly perturb the Cu(II) ligand field. DFT calculations indicated that the higher experimental reoxidation rate observed for the Glu mutant could be reconciled if this residue is protonated. Further, for the glutamic acid form, we identified a Cu(III)-hydroxide species formed in a single step on the H2O2 splitting path. This is in contrast to the Cu(II)-hydroxide and hydroxyl intermediates, which are predicted for the WT and the unprotonated glutamate variant. These results show that this second sphere residue is a crucial determinant of the catalytic functioning of the copper-binding histidine brace and provide insights that may help in understanding LPMOs and LPMO-inspired synthetic catalysts.
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Affiliation(s)
- Kelsi
R. Hall
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Chris Joseph
- Max
Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Iván Ayuso-Fernández
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Ashish Tamhankar
- Max
Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Lukas Rieder
- Institute
for Molecular Biotechnology, Graz University
of Technology, 8010, Graz, Austria
| | - Rannei Skaali
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Ole Golten
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Frank Neese
- Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Åsmund K. Røhr
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Sergio A. V. Jannuzzi
- Max
Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Serena DeBeer
- Max
Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Vincent G. H. Eijsink
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
| | - Morten Sørlie
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), 1432, Ås, Norway
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6
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Torbjörnsson M, Hagemann MM, Ryde U, Hedegård ED. Histidine oxidation in lytic polysaccharide monooxygenase. J Biol Inorg Chem 2023; 28:317-328. [PMID: 36828975 PMCID: PMC10036459 DOI: 10.1007/s00775-023-01993-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 01/10/2023] [Indexed: 02/26/2023]
Abstract
The lytic polysaccharide monooxygenases (LPMOs) comprise a super-family of copper enzymes that boost the depolymerisation of polysaccharides by oxidatively disrupting the glycosidic bonds connecting the sugar units. Industrial use of LPMOs for cellulose depolymerisation has already begun but is still far from reaching its full potential. One issue is that the LPMOs self-oxidise and thereby deactivate. The mechanism of this self-oxidation is unknown, but histidine residues coordinating to the copper atom are the most susceptible. An unusual methyl modification of the NE2 atom in one of the coordinating histidine residues has been proposed to have a protective role. Furthermore, substrate binding is also known to reduce oxidative damage. We here for the first time investigate the mechanism of histidine oxidation with combined quantum and molecular mechanical (QM/MM) calculations, with outset in intermediates previously shown to form from a reaction with peroxide and a reduced LPMO. We show that an intermediate with a [Cu-O]+ moiety is sufficiently potent to oxidise the nearest C-H bond on both histidine residues, but methylation of the NE2 atom of His-1 increases the reaction barrier of this reaction. The substrate further increases the activation barrier. We also investigate a [Cu-OH]2+ intermediate with a deprotonated tyrosine radical. This intermediate was previously proposed to have a protective role, and we also find it to have higher barriers than the corresponding a [Cu-O]+ intermediate.
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Affiliation(s)
- Magne Torbjörnsson
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, 221 00, Lund, Sweden
| | - Marlisa M Hagemann
- Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Ulf Ryde
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, 221 00, Lund, Sweden.
| | - Erik Donovan Hedegård
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, 221 00, Lund, Sweden.
- Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
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7
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Hagemann MM, Hedegård ED. Molecular Mechanism of Substrate Oxidation in Lytic Polysaccharide Monooxygenases: Insight from Theoretical Investigations. Chemistry 2023; 29:e202202379. [PMID: 36207279 PMCID: PMC10107554 DOI: 10.1002/chem.202202379] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Indexed: 12/12/2022]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are copper enzymes that today comprise a large enzyme superfamily, grouped into the distinct members AA9-AA17 (with AA12 exempted). The LPMOs have the potential to facilitate the upcycling of biomass waste products by boosting the breakdown of cellulose and other recalcitrant polysaccharides. The cellulose biopolymer is the main component of biomass waste and thus comprises a large, unexploited resource. The LPMOs work through a catalytic, oxidative reaction whose mechanism is still controversial. For instance, the nature of the intermediate performing the oxidative reaction is an open question, and the same holds for the employed co-substrate. Here we review theoretical investigations addressing these questions. The applied theoretical methods are usually based on quantum mechanics (QM), often combined with molecular mechanics (QM/MM). We discuss advantages and disadvantages of the employed theoretical methods and comment on the interplay between theoretical and experimental results.
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Affiliation(s)
- Marlisa M Hagemann
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense, Denmark
| | - Erik D Hedegård
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense, Denmark
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8
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Schröder GC, O'Dell WB, Webb SP, Agarwal PK, Meilleur F. Capture of activated dioxygen intermediates at the copper-active site of a lytic polysaccharide monooxygenase. Chem Sci 2022; 13:13303-13320. [PMID: 36507176 PMCID: PMC9683017 DOI: 10.1039/d2sc05031e] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 10/19/2022] [Indexed: 11/24/2022] Open
Abstract
Metalloproteins perform a diverse array of redox-related reactions facilitated by the increased chemical functionality afforded by their metallocofactors. Lytic polysaccharide monooxygenases (LPMOs) are a class of copper-dependent enzymes that are responsible for the breakdown of recalcitrant polysaccharides via oxidative cleavage at the glycosidic bond. The activated copper-oxygen intermediates and their mechanism of formation remains to be established. Neutron protein crystallography which permits direct visualization of protonation states was used to investigate the initial steps of oxygen activation directly following active site copper reduction in Neurospora crassa LPMO9D. Herein, we cryo-trap an activated dioxygen intermediate in a mixture of superoxo and hydroperoxo states, and we identify the conserved second coordination shell residue His157 as the proton donor. Density functional theory calculations indicate that both superoxo and hydroperoxo active site states are stable. The hydroperoxo formed is potentially an early LPMO catalytic reaction intermediate or the first step in the mechanism of hydrogen peroxide formation in the absence of substrate. We observe that the N-terminal amino group of the copper coordinating His1 remains doubly protonated directly following molecular oxygen reduction by copper. Aided by molecular dynamics and mining minima free energy calculations we establish that the conserved second-shell His161 in MtPMO3* displays conformational flexibility in solution and that this flexibility is also observed, though to a lesser extent, in His157 of NcLPMO9D. The imidazolate form of His157 observed in our structure following oxygen intermediate protonation can be attributed to abolished His157 flexibility due steric hindrance in the crystal as well as the solvent-occluded active site environment due to crystal packing. A neutron crystal structure of NcLPMO9D at low pH further supports occlusion of the active site since His157 remains singly protonated even at acidic conditions.
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Affiliation(s)
- Gabriela C. Schröder
- Department of Molecular and Structural Biochemistry, North Carolina State UniversityRaleighNC 27695USA,Neutron Scattering Division, Oak Ridge National LaboratoryOak RidgeTN 37831USA
| | - William B. O'Dell
- Department of Molecular and Structural Biochemistry, North Carolina State UniversityRaleighNC 27695USA,Neutron Scattering Division, Oak Ridge National LaboratoryOak RidgeTN 37831USA
| | - Simon P. Webb
- VeraChem LLC12850 Middlebrook Rd. Ste 205GermantownMD 20874-5244USA
| | - Pratul K. Agarwal
- Department of Physiological Sciences and High-Performance Computing Center, Oklahoma State UniversityStillwaterOK 74078USA
| | - Flora Meilleur
- Department of Molecular and Structural Biochemistry, North Carolina State UniversityRaleighNC 27695USA,Neutron Scattering Division, Oak Ridge National LaboratoryOak RidgeTN 37831USA
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9
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Tandrup T, Muderspach SJ, Banerjee S, Santoni G, Ipsen JØ, Hernández-Rollán C, Nørholm MHH, Johansen KS, Meilleur F, Lo Leggio L. Changes in active-site geometry on X-ray photoreduction of a lytic polysaccharide monooxygenase active-site copper and saccharide binding. IUCRJ 2022; 9:666-681. [PMID: 36071795 PMCID: PMC9438499 DOI: 10.1107/s2052252522007175] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 07/12/2022] [Indexed: 06/15/2023]
Abstract
The recently discovered lytic polysaccharide monooxygenases (LPMOs) are Cu-containing enzymes capable of degrading polysaccharide substrates oxidatively. The generally accepted first step in the LPMO reaction is the reduction of the active-site metal ion from Cu2+ to Cu+. Here we have used a systematic diffraction data collection method to monitor structural changes in two AA9 LPMOs, one from Lentinus similis (LsAA9_A) and one from Thermoascus auranti-acus (TaAA9_A), as the active-site Cu is photoreduced in the X-ray beam. For LsAA9_A, the protein produced in two different recombinant systems was crystallized to probe the effect of post-translational modifications and different crystallization conditions on the active site and metal photoreduction. We can recommend that crystallographic studies of AA9 LPMOs wishing to address the Cu2+ form use a total X-ray dose below 3 × 104 Gy, while the Cu+ form can be attained using 1 × 106 Gy. In all cases, we observe the transition from a hexa-coordinated Cu site with two solvent-facing ligands to a T-shaped geometry with no exogenous ligands, and a clear increase of the θ2 parameter and a decrease of the θ3 parameter by averages of 9.2° and 8.4°, respectively, but also a slight increase in θT. Thus, the θ2 and θ3 parameters are helpful diagnostics for the oxidation state of the metal in a His-brace protein. On binding of cello-oligosaccharides to LsAA9_A, regardless of the production source, the θT parameter increases, making the Cu site less planar, while the active-site Tyr-Cu distance decreases reproducibly for the Cu2+ form. Thus, the θT increase found on copper reduction may bring LsAA9_A closer to an oligosaccharide-bound state and contribute to the observed higher affinity of reduced LsAA9_A for cellulosic substrates.
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Affiliation(s)
- Tobias Tandrup
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100-DK, Copenhagen, Denmark
| | - Sebastian J. Muderspach
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100-DK, Copenhagen, Denmark
| | - Sanchari Banerjee
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100-DK, Copenhagen, Denmark
| | - Gianluca Santoni
- ESRF, Structural Biology Group, 71 avenue des Martyrs, 38027 Grenoble cedex, France
| | - Johan Ø. Ipsen
- Department of Geosciences and Natural Resource Management, University of Copenhagen, 1958-DK, Frederiksberg, Denmark
| | - Cristina Hernández-Rollán
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800-DK, Kgs. Lyngby, Denmark
| | - Morten H. H. Nørholm
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800-DK, Kgs. Lyngby, Denmark
| | - Katja S. Johansen
- Department of Geosciences and Natural Resource Management, University of Copenhagen, 1958-DK, Frederiksberg, Denmark
| | - Flora Meilleur
- Department of Molecular and Structural Biochemistry, North Carolina State University, Campus Box 7622, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831, USA
| | - Leila Lo Leggio
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100-DK, Copenhagen, Denmark
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10
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Wang Z, Fang W, Peng W, Wu P, Wang B. Recent Computational Insights into the Oxygen Activation by Copper-Dependent Metalloenzymes. Top Catal 2022. [DOI: 10.1007/s11244-021-01444-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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11
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Sagarika MS, Parameswaran C, Senapati A, Barala J, Mitra D, Prabhukarthikeyan SR, Kumar A, Nayak AK, Panneerselvam P. Lytic polysaccharide monooxygenases (LPMOs) producing microbes: A novel approach for rapid recycling of agricultural wastes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 806:150451. [PMID: 34607097 DOI: 10.1016/j.scitotenv.2021.150451] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 09/12/2021] [Accepted: 09/15/2021] [Indexed: 06/13/2023]
Abstract
Out of the huge quantity of agricultural wastes produced globally, rice straw is one of the most abundant ligno-cellulosic waste. For efficient utilization of these wastes, several cost-effective biological processes are available. The practice of field level in-situ or ex-situ decomposition of rice straw is having less degree of adoption due to its poor decomposition ability within a short time span between rice harvest and sowing of the next crop. Agricultural wastes including rice straw are in general utilized by using lignocellulose degrading microbes for industrial metabolite or compost production. However, bioconversion of crystalline cellulose and lignin present in the waste, into simple molecules is a challenging task. To resolve this issue, researchers have identified a novel new generation microbial enzyme i.e., lytic polysaccharide monooxygenases (LPMOs) and reported that the combination of LPMOs with other glycolytic enzymes are found efficient. This review explains the progress made in LPMOs and their role in lignocellulose bioconversion and the possibility of exploring LPMOs producers for rapid decomposition of agricultural wastes. Also, it provides insights to identify the knowledge gaps in improving the potential of the existing ligno-cellulolytic microbial consortium for efficient utilization of agricultural wastes at industrial and field levels.
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Affiliation(s)
- Mahapatra Smruthi Sagarika
- ICAR - National Rice Research Institute, Cuttack, Odisha 753006, India; Indira Gandhi Agricultural University, Raipur, Chhattisgarh 492012, India
| | | | - Ansuman Senapati
- ICAR - National Rice Research Institute, Cuttack, Odisha 753006, India
| | - Jatiprasad Barala
- ICAR - National Rice Research Institute, Cuttack, Odisha 753006, India
| | - Debasis Mitra
- ICAR - National Rice Research Institute, Cuttack, Odisha 753006, India
| | | | - Anjani Kumar
- ICAR - National Rice Research Institute, Cuttack, Odisha 753006, India
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12
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Zerva A, Pentari C, Ferousi C, Nikolaivits E, Karnaouri A, Topakas E. Recent advances on key enzymatic activities for the utilisation of lignocellulosic biomass. BIORESOURCE TECHNOLOGY 2021; 342:126058. [PMID: 34597805 DOI: 10.1016/j.biortech.2021.126058] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/24/2021] [Accepted: 09/27/2021] [Indexed: 06/13/2023]
Abstract
The field of enzymatic degradation of lignocellulose is actively growing and the recent updates of the last few years indicate that there is still much to learn. The growing number of protein sequences with unknown function in microbial genomes indicates that there is still much to learn on the mechanisms of lignocellulose degradation. In this review, a summary of the progress in the field is presented, including recent discoveries on the nature of the structural polysaccharides, new technologies for the discovery and functional annotation of gene sequences including omics technologies, and the novel lignocellulose-acting enzymes described. Novel enzymatic activities and enzyme families as well as accessory enzymes and their synergistic relationships regarding biomass breakdown are described. Moreover, it is shown that all the valuable knowledge of the enzymatic decomposition of plant biomass polymers can be employed towards the decomposition and upgrading of synthetic polymers, such as plastics.
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Affiliation(s)
- Anastasia Zerva
- Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece
| | - Christina Pentari
- Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece
| | - Christina Ferousi
- Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece
| | - Efstratios Nikolaivits
- Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece
| | - Anthi Karnaouri
- Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece
| | - Evangelos Topakas
- Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece; Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå, Sweden.
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13
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Brander S, Tokin R, Ipsen JØ, Jensen PE, Hernández-Rollán C, Nørholm MHH, Lo Leggio L, Dupree P, Johansen KS. Scission of Glucosidic Bonds by a Lentinus similis Lytic Polysaccharide Monooxygenases Is Strictly Dependent on H2O2 while the Oxidation of Saccharide Products Depends on O2. ACS Catal 2021. [DOI: 10.1021/acscatal.1c04248] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Søren Brander
- Department of Geosciences and Natural Resource Management, Copenhagen University, DK-1958 Frederiksberg, Denmark
| | - Radina Tokin
- Department of Plant and Environmental Sciences, Copenhagen University, DK-1871 Frederiksberg, Denmark
| | - Johan Ø. Ipsen
- Department of Plant and Environmental Sciences, Copenhagen University, DK-1871 Frederiksberg, Denmark
| | - Poul Erik Jensen
- Department of Food Science, University of Copenhagen, Rolighedsvej 26, DK-1958 Frederiksberg, Denmark
| | - Cristina Hernández-Rollán
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Morten H. H. Nørholm
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Leila Lo Leggio
- Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Paul Dupree
- Department of Biochemistry, University of Cambridge, CB2 1QW Cambridge, U.K
| | - Katja S. Johansen
- Department of Geosciences and Natural Resource Management, Copenhagen University, DK-1958 Frederiksberg, Denmark
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14
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Kuusk S, Väljamäe P. Kinetics of H 2O 2-driven catalysis by a lytic polysaccharide monooxygenase from the fungus Trichoderma reesei. J Biol Chem 2021; 297:101256. [PMID: 34597668 PMCID: PMC8528726 DOI: 10.1016/j.jbc.2021.101256] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 09/24/2021] [Accepted: 09/25/2021] [Indexed: 01/17/2023] Open
Abstract
Owing to their ability to break glycosidic bonds in recalcitrant crystalline polysaccharides such as cellulose, the catalysis effected by lytic polysaccharide monooxygenases (LPMOs) is of major interest. Kinetics of these reductant-dependent, monocopper enzymes is complicated by the insoluble nature of the cellulose substrate and parallel, enzyme-dependent, and enzyme-independent side reactions between the reductant and oxygen-containing cosubstrates. Here, we provide kinetic characterization of cellulose peroxygenase (oxidative cleavage of glycosidic bonds in cellulose) and reductant peroxidase (oxidation of the reductant) activities of the LPMO TrAA9A of the cellulose-degrading model fungus Trichoderma reesei. The catalytic efficiency (kcat/Km(H2O2)) of the cellulose peroxygenase reaction (kcat = 8.5 s−1, and Km(H2O2)=30μM) was an order of magnitude higher than that of the reductant (ascorbic acid) peroxidase reaction. The turnover of H2O2 in the ascorbic acid peroxidase reaction followed the ping-pong mechanism and led to irreversible inactivation of the enzyme with a probability of 0.0072. Using theoretical analysis, we suggest a relationship between the half-life of LPMO, the values of kinetic parameters, and the concentrations of the reactants.
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Affiliation(s)
- Silja Kuusk
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia
| | - Priit Väljamäe
- Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia.
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15
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Lee JL, Ross DL, Barman SK, Ziller JW, Borovik AS. C-H Bond Cleavage by Bioinspired Nonheme Metal Complexes. Inorg Chem 2021; 60:13759-13783. [PMID: 34491738 DOI: 10.1021/acs.inorgchem.1c01754] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The functionalization of C-H bonds is one of the most challenging transformations in synthetic chemistry. In biology, these processes are well-known and are achieved with a variety of metalloenzymes, many of which contain a single metal center within their active sites. The most well studied are those with Fe centers, and the emerging experimental data show that high-valent iron oxido species are the intermediates responsible for cleaving the C-H bond. This Forum Article describes the state of this field with an emphasis on nonheme Fe enzymes and current experimental results that provide insights into the properties that make these species capable of C-H bond cleavage. These parameters are also briefly considered in regard to manganese oxido complexes and Cu-containing metalloenzymes. Synthetic iron oxido complexes are discussed to highlight their utility as spectroscopic and mechanistic probes and reagents for C-H bond functionalization. Avenues for future research are also examined.
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Affiliation(s)
- Justin L Lee
- Department of Chemistry, University of California-Irvine, 1102 Natural Sciences II, Irvine, California 92697, United States
| | - Dolores L Ross
- Department of Chemistry, University of California-Irvine, 1102 Natural Sciences II, Irvine, California 92697, United States
| | - Suman K Barman
- Department of Chemistry, University of California-Irvine, 1102 Natural Sciences II, Irvine, California 92697, United States
| | - Joseph W Ziller
- Department of Chemistry, University of California-Irvine, 1102 Natural Sciences II, Irvine, California 92697, United States
| | - A S Borovik
- Department of Chemistry, University of California-Irvine, 1102 Natural Sciences II, Irvine, California 92697, United States
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16
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Sethupathy S, Morales GM, Li Y, Wang Y, Jiang J, Sun J, Zhu D. Harnessing microbial wealth for lignocellulose biomass valorization through secretomics: a review. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:154. [PMID: 34225772 PMCID: PMC8256616 DOI: 10.1186/s13068-021-02006-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 06/26/2021] [Indexed: 05/10/2023]
Abstract
The recalcitrance of lignocellulosic biomass is a major constraint to its high-value use at industrial scale. In nature, microbes play a crucial role in biomass degradation, nutrient recycling and ecosystem functioning. Therefore, the use of microbes is an attractive way to transform biomass to produce clean energy and high-value compounds. The microbial degradation of lignocelluloses is a complex process which is dependent upon multiple secreted enzymes and their synergistic activities. The availability of the cutting edge proteomics and highly sensitive mass spectrometry tools make possible for researchers to probe the secretome of microbes and microbial consortia grown on different lignocelluloses for the identification of hydrolytic enzymes of industrial interest and their substrate-dependent expression. This review summarizes the role of secretomics in identifying enzymes involved in lignocelluloses deconstruction, the development of enzyme cocktails and the construction of synthetic microbial consortia for biomass valorization, providing our perspectives to address the current challenges.
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Affiliation(s)
- Sivasamy Sethupathy
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Gabriel Murillo Morales
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Yixuan Li
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Yongli Wang
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Jianxiong Jiang
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Jianzhong Sun
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China
| | - Daochen Zhu
- School of the Environment and Safety Engineering, Biofuels Institute, Jiangsu University, Zhenjiang, 212013, Jiangsu, China.
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17
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Wu T, Musgrove J, Siegler MA, Garcia-Bosch I. Mononuclear and Dinuclear Copper Complexes of Tridentate Redox-active Ligands with Tunable H-bonding Donors: Structure, Spectroscopy and H + /e - Reactivity. Chem Asian J 2021; 16:1608-1618. [PMID: 33929787 DOI: 10.1002/asia.202100286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 04/29/2021] [Indexed: 11/06/2022]
Abstract
In this research article, we describe the synthesis and characterization of mononuclear and dinuclear Cu complexes bound by a family of tridentate redox-active ligands with tunable H-bonding donors. The mononuclear Cu-anion complexes were oxidized to the corresponding "high-valent" intermediates by oxidation of the redox-active ligand. These species were capable of oxidizing phenols with weak O-H bonds via H-atom abstraction. Thermodynamic analysis of the H-atom abstractions, which included reduction potential measurements, pKa determination and kinetic studies, revealed that modification of the anion coordinated to the Cu and changes in the H-bonding donor did not lead to major differences in the reactivity of the "high-valent" CuY complexes (Y: hydroxide, phenolate and acetate), which indicated that the tridentate ligand scaffold acts as the H+ and e- acceptor.
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Affiliation(s)
- Tong Wu
- Department of Chemistry, Southern Methodist University, Dallas, Texas, 75275, United States
| | - Justin Musgrove
- Department of Chemistry, Southern Methodist University, Dallas, Texas, 75275, United States
| | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland, 21218, United States
| | - Isaac Garcia-Bosch
- Department of Chemistry, Southern Methodist University, Dallas, Texas, 75275, United States
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18
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Hedison TM, Breslmayr E, Shanmugam M, Karnpakdee K, Heyes DJ, Green AP, Ludwig R, Scrutton NS, Kracher D. Insights into the H 2 O 2 -driven catalytic mechanism of fungal lytic polysaccharide monooxygenases. FEBS J 2021; 288:4115-4128. [PMID: 33411405 PMCID: PMC8359147 DOI: 10.1111/febs.15704] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 12/09/2020] [Accepted: 01/05/2021] [Indexed: 12/20/2022]
Abstract
Fungal lytic polysaccharide monooxygenases (LPMOs) depolymerise crystalline cellulose and hemicellulose, supporting the utilisation of lignocellulosic biomass as a feedstock for biorefinery and biomanufacturing processes. Recent investigations have shown that H2O2 is the most efficient cosubstrate for LPMOs. Understanding the reaction mechanism of LPMOs with H2O2 is therefore of importance for their use in biotechnological settings. Here, we have employed a variety of spectroscopic and biochemical approaches to probe the reaction of the fungal LPMO9C from N. crassa using H2O2 as a cosubstrate and xyloglucan as a polysaccharide substrate. We show that a single ‘priming’ electron transfer reaction from the cellobiose dehydrogenase partner protein supports up to 20 H2O2‐driven catalytic cycles of a fungal LPMO. Using rapid mixing stopped‐flow spectroscopy, alongside electron paramagnetic resonance and UV‐Vis spectroscopy, we reveal how H2O2 and xyloglucan interact with the enzyme and investigate transient species that form uncoupled pathways of NcLPMO9C. Our study shows how the H2O2 cosubstrate supports fungal LPMO catalysis and leaves the enzyme in the reduced Cu+ state following a single enzyme turnover, thus preventing the need for external protons and electrons from reducing agents or cellobiose dehydrogenase and supporting the binding of H2O2 for further catalytic steps. We observe that the presence of the substrate xyloglucan stabilises the Cu+ state of LPMOs, which may prevent the formation of uncoupled side reactions.
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Affiliation(s)
- Tobias M Hedison
- Manchester Institute of Biotechnology, The University of Manchester, UK.,Future Biomanufacturing Research Hub, Manchester Institute of Biotechnology, The University of Manchester, UK
| | - Erik Breslmayr
- Manchester Institute of Biotechnology, The University of Manchester, UK.,Biocatalysis and Biosensing Laboratory, Department of Food Science and Technology, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Muralidharan Shanmugam
- Manchester Institute of Biotechnology, The University of Manchester, UK.,Photon Science Institute, The University of Manchester, UK
| | - Kwankao Karnpakdee
- Biocatalysis and Biosensing Laboratory, Department of Food Science and Technology, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Derren J Heyes
- Manchester Institute of Biotechnology, The University of Manchester, UK
| | - Anthony P Green
- Manchester Institute of Biotechnology, The University of Manchester, UK.,Future Biomanufacturing Research Hub, Manchester Institute of Biotechnology, The University of Manchester, UK
| | - Roland Ludwig
- Biocatalysis and Biosensing Laboratory, Department of Food Science and Technology, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Nigel S Scrutton
- Manchester Institute of Biotechnology, The University of Manchester, UK.,Future Biomanufacturing Research Hub, Manchester Institute of Biotechnology, The University of Manchester, UK
| | - Daniel Kracher
- Manchester Institute of Biotechnology, The University of Manchester, UK.,Biocatalysis and Biosensing Laboratory, Department of Food Science and Technology, University of Natural Resources and Life Sciences, Vienna, Austria
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19
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Dodge N, Russo DA, Blossom BM, Singh RK, van Oort B, Croce R, Bjerrum MJ, Jensen PE. Water-soluble chlorophyll-binding proteins from Brassica oleracea allow for stable photobiocatalytic oxidation of cellulose by a lytic polysaccharide monooxygenase. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:192. [PMID: 33292428 PMCID: PMC7708235 DOI: 10.1186/s13068-020-01832-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 11/16/2020] [Indexed: 05/06/2023]
Abstract
BACKGROUND Lytic polysaccharide monooxygenases (LPMOs) are indispensable redox enzymes used in industry for the saccharification of plant biomass. LPMO-driven cellulose oxidation can be enhanced considerably through photobiocatalysis using chlorophyll derivatives and light. Water soluble chlorophyll binding proteins (WSCPs) make it is possible to stabilize and solubilize chlorophyll in aqueous solution, allowing for in vitro studies on photostability and ROS production. Here we aim to apply WSCP-Chl a as a photosensitizing complex for photobiocatalysis with the LPMO, TtAA9. RESULTS We have in this study demonstrated how WSCP reconstituted with chlorophyll a (WSCP-Chl a) can create a stable photosensitizing complex which produces controlled amounts of H2O2 in the presence of ascorbic acid and light. WSCP-Chl a is highly reactive and allows for tightly controlled formation of H2O2 by regulating light intensity. TtAA9 together with WSCP-Chl a shows increased cellulose oxidation under low light conditions, and the WSCP-Chl a complex remains stable after 24 h of light exposure. Additionally, the WSCP-Chl a complex demonstrates stability over a range of temperatures and pH conditions relevant for enzyme activity in industrial settings. CONCLUSION With WSCP-Chl a as the photosensitizer, the need to replenish Chl is greatly reduced, enhancing the catalytic lifetime of light-driven LPMOs and increasing the efficiency of cellulose depolymerization. WSCP-Chl a allows for stable photobiocatalysis providing a sustainable solution for biomass processing.
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Affiliation(s)
- N Dodge
- Department of Food Science, University of Copenhagen, Rolighedsvej 26, 1958, Frederiksberg, Denmark
| | - D A Russo
- Department of Bioorganic Analytics, Institute for Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Jena, Germany
| | - B M Blossom
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Frederiksberg C, Denmark
| | - R K Singh
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - B van Oort
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - R Croce
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, and LaserLaB Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - M J Bjerrum
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - P E Jensen
- Department of Food Science, University of Copenhagen, Rolighedsvej 26, 1958, Frederiksberg, Denmark.
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20
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McEvoy A, Creutzberg J, Singh RK, Bjerrum MJ, Hedegård ED. The role of the active site tyrosine in the mechanism of lytic polysaccharide monooxygenase. Chem Sci 2020; 12:352-362. [PMID: 34163601 PMCID: PMC8178957 DOI: 10.1039/d0sc05262k] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Catalytic breakdown of polysaccharides can be achieved more efficiently by means of the enzymes lytic polysaccharide monooxygenases (LPMOs). However, the LPMO mechanism has remained controversial, preventing full exploitation of their potential. One of the controversies has centered around an active site tyrosine, present in most LPMO classes. Recent investigations have for the first time obtained direct (spectroscopic) evidence for the possibility of chemical modification of this tyrosine. However, the spectroscopic features obtained in the different investigations are remarkably different, with absorption maximum at 420 and 490 nm, respectively. In this paper we use density functional theory (DFT) in a QM/MM formulation to reconcile these (apparently) conflicting results. By modeling the spectroscopy as well as the underlying reaction mechanism we can show how formation of two isomers (both involving deprotonation of tyrosine) explains the difference in the observed spectroscopic features. Both isomers have a [TyrO–Cu–OH]+ moiety with the OH in either the cis- or trans-position to a deprotonated tyrosine. Although the cis-[TyrO–Cu–OH]+ moiety is well positioned for oxidation of the substrate, preliminary calculations with the substrate reveal that the reactivity is at best moderate, making a protective role of tyrosine more likely. With QM/MM, we investigate the mechanism of tyrosine deprotonation in lytic polysaccharide monooxygenases. Our results support deprotonation and our calculated UV-vis spectra show that two isomers must be formed to match recent experiments.![]()
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Affiliation(s)
- Aina McEvoy
- Division of Theoretical Chemistry, Lund University Box 124 SE-221 00 Lund Sweden
| | - Joel Creutzberg
- Division of Theoretical Chemistry, Lund University Box 124 SE-221 00 Lund Sweden
| | - Raushan K Singh
- Department of Chemistry, University of Copenhagen Copenhagen Denmark
| | - Morten J Bjerrum
- Department of Chemistry, University of Copenhagen Copenhagen Denmark
| | - Erik D Hedegård
- Division of Theoretical Chemistry, Lund University Box 124 SE-221 00 Lund Sweden
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21
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Wang B, Wang Z, Davies GJ, Walton PH, Rovira C. Activation of O2 and H2O2 by Lytic Polysaccharide Monooxygenases. ACS Catal 2020. [DOI: 10.1021/acscatal.0c02914] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Binju Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People’s Republic of China
| | - Zhanfeng Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People’s Republic of China
| | - Gideon J. Davies
- Department of Chemistry, University of York, Heslington, YO10 5DD, U.K
| | - Paul H. Walton
- Department of Chemistry, University of York, Heslington, YO10 5DD, U.K
| | - Carme Rovira
- Departament de Quı́mica Inorgànica i Orgànica & IQTCUB, Universitat de Barcelona, Martı́ i Franquès 1, 08028 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluı́s Companys, 23, 08020 Barcelona, Spain
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22
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Brander S, Horvath I, Ipsen JØ, Peciulyte A, Olsson L, Hernández-Rollán C, Nørholm MHH, Mossin S, Leggio LL, Probst C, Thiele DJ, Johansen KS. Biochemical evidence of both copper chelation and oxygenase activity at the histidine brace. Sci Rep 2020; 10:16369. [PMID: 33004835 PMCID: PMC7529816 DOI: 10.1038/s41598-020-73266-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 09/15/2020] [Indexed: 12/22/2022] Open
Abstract
Lytic polysaccharide monooxygenase (LPMO) and copper binding protein CopC share a similar mononuclear copper site. This site is defined by an N-terminal histidine and a second internal histidine side chain in a configuration called the histidine brace. To understand better the determinants of reactivity, the biochemical and structural properties of a well-described cellulose-specific LPMO from Thermoascus aurantiacus (TaAA9A) is compared with that of CopC from Pseudomonas fluorescens (PfCopC) and with the LPMO-like protein Bim1 from Cryptococcus neoformans. PfCopC is not reduced by ascorbate but is a very strong Cu(II) chelator due to residues that interacts with the N-terminus. This first biochemical characterization of Bim1 shows that it is not redox active, but very sensitive to H2O2, which accelerates the release of Cu ions from the protein. TaAA9A oxidizes ascorbate at a rate similar to free copper but through a mechanism that produce fewer reactive oxygen species. These three biologically relevant examples emphasize the diversity in how the proteinaceous environment control reactivity of Cu with O2.
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Affiliation(s)
- Søren Brander
- Department of Geoscience and Natural Resource Management, University of Copenhagen, 1958, Frederiksberg, Denmark
| | - Istvan Horvath
- Division of Chemical Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Johan Ø Ipsen
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg, Denmark
| | - Ausra Peciulyte
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Lisbeth Olsson
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Cristina Hernández-Rollán
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
| | - Morten H H Nørholm
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
| | - Susanne Mossin
- Centre for Catalysis and Sustainable Chemistry, Department of Chemistry, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
| | - Leila Lo Leggio
- Department of Chemistry, University of Copenhagen, 2100, Copenhagen Ø, Denmark
| | - Corinna Probst
- Department of Biochemistry, Pharmacology and Cancer Biology and Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Dennis J Thiele
- Department of Biochemistry, Pharmacology and Cancer Biology and Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Katja S Johansen
- Department of Geoscience and Natural Resource Management, University of Copenhagen, 1958, Frederiksberg, Denmark. .,Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden.
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23
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Wu T, MacMillan SN, Rajabimoghadam K, Siegler MA, Lancaster KM, Garcia-Bosch I. Structure, Spectroscopy, and Reactivity of a Mononuclear Copper Hydroxide Complex in Three Molecular Oxidation States. J Am Chem Soc 2020; 142:12265-12276. [PMID: 32531159 DOI: 10.1021/jacs.0c03867] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Structural, spectroscopic, and reactivity studies are presented for an electron transfer series of copper hydroxide complexes supported by a tridentate redox-active ligand. Single crystal X-ray crystallography shows that the mononuclear [CuOH]1+ core is stabilized via intramolecular H-bonds between the H-donors of the ligand and the hydroxide anion when the ligand is in its trianionic form. This complex undergoes two reversible oxidation processes that produce two metastable "high-valent" CuOH species, which can be generated by addition of stoichiometric amounts of 1e- oxidants. These CuOH species are characterized by an array of spectroscopic techniques including UV-vis absorption, electron paramagnetic resonance (EPR), and X-ray absorption spectroscopies (XAS), which together indicate that all redox couples are ligand-localized. The reactivity of the complexes in their higher oxidation states toward substrates with modest O-H bond dissociation energies (e.g., 4-substitued-2,6-di-tert-butylphenols) indicates that these complexes act as 2H+/2e- oxidants, differing from the 1H+/1e- reactivity of well-studied [CuOH]2+ systems.
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Affiliation(s)
- Tong Wu
- Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States
| | - Samantha N MacMillan
- Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853, United States
| | | | - Maxime A Siegler
- Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853, United States
| | - Isaac Garcia-Bosch
- Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States
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24
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Cripwell RA, Favaro L, Viljoen-Bloom M, van Zyl WH. Consolidated bioprocessing of raw starch to ethanol by Saccharomyces cerevisiae: Achievements and challenges. Biotechnol Adv 2020; 42:107579. [PMID: 32593775 DOI: 10.1016/j.biotechadv.2020.107579] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 06/05/2020] [Accepted: 06/14/2020] [Indexed: 12/30/2022]
Abstract
Recent advances in amylolytic strain engineering for starch-to-ethanol conversion have provided a platform for the development of raw starch consolidated bioprocessing (CBP) technologies. Several proof-of-concept studies identified improved enzyme combinations, alternative feedstocks and novel host strains for evaluation and application under fermentation conditions. However, further research efforts are required before this technology can be scaled up to an industrial level. In this review, different CBP approaches are defined and discussed, also highlighting the role of auxiliary enzymes for a supplemented CBP process. Various achievements in the development of amylolytic Saccharomyces cerevisiae strains for CBP of raw starch and the remaining challenges that need to be tackled/pursued to bring yeast raw starch CBP to industrial realization, are described. Looking towards the future, it provides potential solutions to develop more cost-effective processes that include cheaper substrates, integration of the 1G and 2G economies and implementing a biorefinery concept where high-value products are also derived from starchy substrates.
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Affiliation(s)
- Rosemary A Cripwell
- Department of Microbiology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Lorenzo Favaro
- Department of Agronomy Food Natural resources Animals and Environment (DAFNAE), Università di Padova, Agripolis, Viale dell'Università 16, 35020, Legnaro, Padova, Italy
| | - Marinda Viljoen-Bloom
- Department of Microbiology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Willem H van Zyl
- Department of Microbiology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa.
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25
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Purification and characterization of a native lytic polysaccharide monooxygenase from Thermoascus aurantiacus. Biotechnol Lett 2020; 42:1897-1905. [DOI: 10.1007/s10529-020-02942-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 06/11/2020] [Indexed: 01/23/2023]
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Kinetic analysis of amino acid radicals formed in H 2O 2-driven Cu I LPMO reoxidation implicates dominant homolytic reactivity. Proc Natl Acad Sci U S A 2020; 117:11916-11922. [PMID: 32414932 PMCID: PMC7275769 DOI: 10.1073/pnas.1922499117] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Lytic polysaccharide monooxygenases (LPMOs) have been proposed to react with both [Formula: see text] and [Formula: see text] as cosubstrates. In this study, the [Formula: see text] reaction with reduced Hypocrea jecorina LPMO9A (CuI-HjLPMO9A) is demonstrated to be 1,000-fold faster than the [Formula: see text] reaction while producing the same oxidized oligosaccharide products. Analysis of the reactivity in the absence of polysaccharide substrate by stopped-flow absorption and rapid freeze-quench (RFQ) electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) yields two intermediates corresponding to neutral tyrosyl and tryptophanyl radicals that are formed along minor reaction pathways. The dominant reaction pathway is characterized by RFQ EPR and kinetic modeling to directly produce CuII-HjLPMO9A and indicates homolytic O-O cleavage. Both optical intermediates exhibit magnetic exchange coupling with the CuII sites reflecting facile electron transfer (ET) pathways, which may be protective against uncoupled turnover or provide an ET pathway to the active site with substrate bound. The reactivities of nonnative organic peroxide cosubstrates effectively exclude the possibility of a ping-pong mechanism.
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27
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Zhou X, Zhu H. Current understanding of substrate specificity and regioselectivity of LPMOs. BIORESOUR BIOPROCESS 2020. [DOI: 10.1186/s40643-020-0300-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
AbstractRenewable biomass such as cellulose and chitin are the most abundant sustainable sources of energy and materials. However, due to the low degradation efficiency of these recalcitrant substrates by conventional hydrolases, these biomass resources cannot be utilized efficiently. In 2010, the discovery of lytic polysaccharide monooxygenases (LPMOs) led to a major breakthrough. Currently, LPMOs are distributed in 7 families in CAZy database, including AA9–11 and AA13–16, with different species origins, substrate specificity and oxidative regioselectivity. Effective application of LPMOs in the biotransformation of biomass resources needs the elucidation of the molecular basis of their function. Since the discovery of LPMOs, great advances have been made in the study of their substrate specificity and regioselectivity, as well as their structural basis, which will be reviewed below.
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28
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Breslmayr E, Daly S, Požgajčić A, Chang H, Rezić T, Oostenbrink C, Ludwig R. Improved spectrophotometric assay for lytic polysaccharide monooxygenase. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:283. [PMID: 31827611 PMCID: PMC6894463 DOI: 10.1186/s13068-019-1624-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 11/28/2019] [Indexed: 05/31/2023]
Abstract
BACKGROUND The availability of a sensitive and robust activity assay is a prerequisite for efficient enzyme production, purification, and characterization. Here we report on a spectrophotometric assay for lytic polysaccharide monooxygenase (LPMO), which is an advancement of the previously published 2,6-dimethoxyphenol (2,6-DMP)-based LPMO assay. The new assay is based on hydrocoerulignone as substrate and hydrogen peroxide as cosubstrate and aims toward a higher sensitivity at acidic pH and a more reliable detection of LPMO in complex matrices like culture media. RESULTS An LPMO activity assay following the colorimetric oxidation of hydrocoerulignone to coerulignone was developed. This peroxidase activity of LPMO in the presence of hydrogen peroxide can be detected in various buffers between pH 4-8. By reducing the substrate and cosubstrate concentration, the assay has been optimized for minimal autoxidation and enzyme deactivation while maintaining sensitivity. Finally, the optimized and validated LPMO assay was used to follow the recombinant expression of an LPMO in Pichia pastoris and to screen for interfering substances in fermentation media suppressing the assayed reaction. CONCLUSIONS The biphenol hydrocoerulignone is a better substrate for LPMO than the monophenol 2,6-DMP, because of a ~ 30 times lower apparent K M value and a 160 mV lower oxidation potential. This greatly increases the measured LPMO activity when using hydrocoerulignone instead of 2,6-DMP under otherwise similar assay conditions. The improved activity allows the adaptation of the LPMO assay toward a higher sensitivity, different buffers and pH values, more stable assay conditions or to overcome low concentrations of inhibiting substances. The developed assay protocol and optimization guidelines increase the adaptability and applicability of the hydrocoerulignone assay for the production, purification, and characterization of LPMOs.
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Affiliation(s)
- Erik Breslmayr
- Biocatalysis and Biosensor Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
- Institute of Molecular Modeling and Simulation, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
| | - Sarah Daly
- Biocatalysis and Biosensor Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
| | - Alen Požgajčić
- Biocatalysis and Biosensor Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
- Department of Biochemical Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia
| | - Hucheng Chang
- Biocatalysis and Biosensor Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
| | - Tonči Rezić
- Department of Biochemical Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia
| | - Chris Oostenbrink
- Institute of Molecular Modeling and Simulation, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
| | - Roland Ludwig
- Biocatalysis and Biosensor Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
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29
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Paradisi A, Johnston EM, Tovborg M, Nicoll CR, Ciano L, Dowle A, McMaster J, Hancock Y, Davies GJ, Walton PH. Formation of a Copper(II)-Tyrosyl Complex at the Active Site of Lytic Polysaccharide Monooxygenases Following Oxidation by H 2O 2. J Am Chem Soc 2019; 141:18585-18599. [PMID: 31675221 PMCID: PMC7007232 DOI: 10.1021/jacs.9b09833] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Indexed: 01/14/2023]
Abstract
Hydrogen peroxide is a cosubstrate for the oxidative cleavage of saccharidic substrates by copper-containing lytic polysaccharide monooxygenases (LPMOs). The rate of reaction of LPMOs with hydrogen peroxide is high, but it is accompanied by rapid inactivation of the enzymes, presumably through protein oxidation. Herein, we use UV-vis, CD, XAS, EPR, VT/VH-MCD, and resonance Raman spectroscopies, augmented with mass spectrometry and DFT calculations, to show that the product of reaction of an AA9 LPMO with H2O2 at higher pHs is a singlet Cu(II)-tyrosyl radical species, which is inactive for the oxidation of saccharidic substrates. The Cu(II)-tyrosyl radical center entails the formation of significant Cu(II)-(●OTyr) overlap, which in turn requires that the plane of the d(x2-y2) SOMO of the Cu(II) is orientated toward the tyrosyl radical. We propose from the Marcus cross-relation that the active site tyrosine is part of a "hole-hopping" charge-transfer mechanism formed of a pathway of conserved tyrosine and tryptophan residues, which can protect the protein active site from inactivation during uncoupled turnover.
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Affiliation(s)
- Alessandro Paradisi
- Department
of Chemistry, Centre of Excellence of Mass Spectrometry, Technology
Facility, and Department of Physics, University of York, Heslington, York YO10
5DD, United Kingdom
| | - Esther M. Johnston
- Department
of Chemistry, Centre of Excellence of Mass Spectrometry, Technology
Facility, and Department of Physics, University of York, Heslington, York YO10
5DD, United Kingdom
| | | | - Callum R. Nicoll
- Department
of Chemistry, Centre of Excellence of Mass Spectrometry, Technology
Facility, and Department of Physics, University of York, Heslington, York YO10
5DD, United Kingdom
| | - Luisa Ciano
- Department
of Chemistry, Centre of Excellence of Mass Spectrometry, Technology
Facility, and Department of Physics, University of York, Heslington, York YO10
5DD, United Kingdom
| | - Adam Dowle
- Department
of Chemistry, Centre of Excellence of Mass Spectrometry, Technology
Facility, and Department of Physics, University of York, Heslington, York YO10
5DD, United Kingdom
| | - Jonathan McMaster
- School
of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
| | - Y. Hancock
- Department
of Chemistry, Centre of Excellence of Mass Spectrometry, Technology
Facility, and Department of Physics, University of York, Heslington, York YO10
5DD, United Kingdom
- York
Cross-Disciplinary Centre for Systems Analysis, University of York, Heslington,
York YO10 5GE, United Kingdom
| | - Gideon J. Davies
- Department
of Chemistry, Centre of Excellence of Mass Spectrometry, Technology
Facility, and Department of Physics, University of York, Heslington, York YO10
5DD, United Kingdom
| | - Paul H. Walton
- Department
of Chemistry, Centre of Excellence of Mass Spectrometry, Technology
Facility, and Department of Physics, University of York, Heslington, York YO10
5DD, United Kingdom
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