1
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Hall K, Mollatt M, Forsberg Z, Golten O, Schwaiger L, Ludwig R, Ayuso-Fernández I, Eijsink VGH, Sørlie M. Impact of the Copper Second Coordination Sphere on Catalytic Performance and Substrate Specificity of a Bacterial Lytic Polysaccharide Monooxygenase. ACS OMEGA 2024; 9:23040-23052. [PMID: 38826537 PMCID: PMC11137697 DOI: 10.1021/acsomega.4c02666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 04/26/2024] [Accepted: 04/30/2024] [Indexed: 06/04/2024]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of glycosidic bonds in recalcitrant polysaccharides, such as cellulose and chitin, using a single copper cofactor bound in a conserved histidine brace with a more variable second coordination sphere. Cellulose-active LPMOs in the fungal AA9 family and in a subset of bacterial AA10 enzymes contain a His-Gln-Tyr second sphere motif, whereas other cellulose-active AA10s have an Arg-Glu-Phe motif. To shine a light on the impact of this variation, we generated single, double, and triple mutations changing the His216-Gln219-Tyr221 motif in cellulose- and chitin-oxidizing MaAA10B toward Arg-Glu-Phe. These mutations generally reduced enzyme performance due to rapid inactivation under turnover conditions, showing that catalytic fine-tuning of the histidine brace is complex and that the roles of these second sphere residues are strongly interconnected. Studies of copper reactivity showed remarkable effects, such as an increase in oxidase activity following the Q219E mutation and a strong dependence of this effect on the presence of Tyr at position 221. In reductant-driven reactions, differences in oxidase activity, which lead to different levels of in situ generated H2O2, correlated with differences in polysaccharide-degrading ability. The single Q219E mutant displayed a marked increase in activity on chitin in both reductant-driven reactions and reactions fueled by exogenously added H2O2. Thus, it seems that the evolution of substrate specificity in LPMOs involves both the extended substrate-binding surface and the second coordination sphere.
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Affiliation(s)
- Kelsi
R. Hall
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås 1432, Norway
- School
of Biological Sciences, University of Canterbury, Christchurch 8140, New Zealand
| | - Maja Mollatt
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås 1432, Norway
| | - Zarah Forsberg
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås 1432, Norway
| | - Ole Golten
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås 1432, Norway
| | - Lorenz Schwaiger
- Department
of Food Science and Technology, Institute of Food Technology, University of Natural Resources and Life Sciences, Vienna, BOKU 1190 Vienna, Austria
| | - Roland Ludwig
- Department
of Food Science and Technology, Institute of Food Technology, University of Natural Resources and Life Sciences, Vienna, BOKU 1190 Vienna, Austria
| | - Iván Ayuso-Fernández
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås 1432, Norway
| | - Vincent G. H. Eijsink
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås 1432, Norway
| | - Morten Sørlie
- Faculty
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), Ås 1432, Norway
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2
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Wieduwilt EK, Lo Leggio L, Hedegård ED. A frontier-orbital view of the initial steps of lytic polysaccharide monooxygenase reactions. Dalton Trans 2024; 53:5796-5807. [PMID: 38445349 DOI: 10.1039/d3dt04275h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2024]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are copper enzymes that oxidatively cleave the strong C-H bonds in recalcitrant polysaccharide substrates, thereby playing a crucial role in biomass degradation. Recently, LPMOs have also been shown to be important for several pathogens. It is well established that the Cu(II) resting state of LPMOs is inactive, and the electronic structure of the active site needs to be altered to transform the enzyme into an active form. Whether this transformation occurs due to substrate binding or due to a unique priming reduction has remained speculative. Starting from four different crystal structures of the LPMO LsAA9A with well-defined oxidation states, we use a frontier molecular orbital approach to elucidate the initial steps of the LPMO reaction. We give an explanation for the requirement of the unique priming reduction and analyse electronic structure changes upon substrate binding. We further investigate how the presence of the substrate could facilitate an electron transfer from the copper active site to an H2O2 co-substrate. Our findings could help to control experimental LPMO reactions.
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Affiliation(s)
- Erna Katharina Wieduwilt
- Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
| | - Leila Lo Leggio
- Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Erik Donovan Hedegård
- Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
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3
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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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4
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Lim H, Brueggemeyer MT, Transue WJ, Meier KK, Jones SM, Kroll T, Sokaras D, Kelemen B, Hedman B, Hodgson KO, Solomon EI. Kβ X-ray Emission Spectroscopy of Cu(I)-Lytic Polysaccharide Monooxygenase: Direct Observation of the Frontier Molecular Orbital for H 2O 2 Activation. J Am Chem Soc 2023; 145:16015-16025. [PMID: 37441786 PMCID: PMC10557184 DOI: 10.1021/jacs.3c04048] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/15/2023]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) catalyze the degradation of recalcitrant carbohydrate polysaccharide substrates. These enzymes are characterized by a mononuclear Cu(I) active site with a three-coordinate T-shaped "His-brace" configuration including the N-terminal histidine and its amine group as ligands. This study explicitly investigates the electronic structure of the d10 Cu(I) active site in a LPMO using Kβ X-ray emission spectroscopy (XES). The lack of inversion symmetry in the His-brace site enables the 3d/p mixing required for intensity in the Kβ valence-to-core (VtC) XES spectrum of Cu(I)-LPMO. These Kβ XES data are correlated to density functional theory (DFT) calculations to define the bonding, and in particular, the frontier molecular orbital (FMO) of the Cu(I) site. These experimentally validated DFT calculations are used to evaluate the reaction coordinate for homolytic cleavage of the H2O2 O-O bond and understand the contribution of this FMO to the low barrier of this reaction and how the geometric and electronic structure of the Cu(I)-LPMO site is activated for rapid reactivity with H2O2.
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Affiliation(s)
- Hyeongtaek Lim
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | | | - Wesley J Transue
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Katlyn K Meier
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Stephen M Jones
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Bradley Kelemen
- IFF Health and Biosciences, Palo Alto, California 94304, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
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5
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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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6
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Ngo ST, Phan HN, Luu CX, Le CN, Ho GT, Ngo NTC, Le LQ, Mai BK, Phung HTT, Nguyen HD, Vu KB, Vu VV. Distal Hydrophobic Loop Modulates the Copper Active Site and Reaction of AA13 Polysaccharide Monooxygenases. J Phys Chem B 2022; 126:7567-7578. [PMID: 36137238 DOI: 10.1021/acs.jpcb.2c04215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Polysaccharide monooxygenases (PMOs) use a type-2 copper center to activate O2 for the selective hydroxylation of one of the two C-H bonds of glycosidic linkages. Our electron paramagnetic resonance (EPR) analysis and molecular dynamics (MD) simulations suggest the unprecedented dynamic roles of the loop containing the residue G89 (G89 loop) on the active site structure and reaction cycle of starch-active PMOs (AA13 PMOs). In the Cu(II) state, the G89 loop could switch between an "open" and "closed" conformation, which is associated with the binding and dissociation of an aqueous ligand in the distal site, respectively. The conformation of the G89 loop influences the positioning of the copper center on the preferred substrate of AA13 PMOs. The dissociation of the distal ligand results in the bending of the T-shaped core of the Cu(II) active site, which could help facilitate its reduction to the active Cu(I) state. In the Cu(I) state, the G89 loop is in the "closed" conformation with a confined copper center, which could allow for efficient O2 binding. In addition, the G89 loop remains in the "closed" conformation in the Cu(II)-superoxo intermediate, which could prevent off-pathway superoxide release via exchange with the distal aqueous ligand. Finally, at the end of the reaction cycle, aqueous ligand binding to the distal site could switch the G89 loop to the "open" conformation and facilitate product release.
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Affiliation(s)
- Son Tung Ngo
- Laboratory of Theoretical and Computational Biophysics, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam.,Faculty of Pharmacy, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
| | - Han N Phan
- NTT Hi-Tech Institute, Nguyen Tat Thanh University, 298-300A Nguyen Tat Thanh Street, District 4, Ho Chi Minh City 700000, Vietnam
| | - Cuong X Luu
- NTT Hi-Tech Institute, Nguyen Tat Thanh University, 298-300A Nguyen Tat Thanh Street, District 4, Ho Chi Minh City 700000, Vietnam
| | - Chinh N Le
- NTT Hi-Tech Institute, Nguyen Tat Thanh University, 298-300A Nguyen Tat Thanh Street, District 4, Ho Chi Minh City 700000, Vietnam
| | - Giap T Ho
- NTT Hi-Tech Institute, Nguyen Tat Thanh University, 298-300A Nguyen Tat Thanh Street, District 4, Ho Chi Minh City 700000, Vietnam
| | - Nhung T C Ngo
- NTT Hi-Tech Institute, Nguyen Tat Thanh University, 298-300A Nguyen Tat Thanh Street, District 4, Ho Chi Minh City 700000, Vietnam
| | - Loan Q Le
- Institute of Tropical Biology, Vietnam Academy of Science and Technology, 9/621 Hanoi Highway, Thu Duc District, Ho Chi Minh City 700000, Vietnam
| | - Binh Khanh Mai
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm SE-106 91, Sweden
| | - Huong T T Phung
- NTT Hi-Tech Institute, Nguyen Tat Thanh University, 298-300A Nguyen Tat Thanh Street, District 4, Ho Chi Minh City 700000, Vietnam
| | - Hoang-Dung Nguyen
- NTT Hi-Tech Institute, Nguyen Tat Thanh University, 298-300A Nguyen Tat Thanh Street, District 4, Ho Chi Minh City 700000, Vietnam.,Institute of Tropical Biology, Vietnam Academy of Science and Technology, 9/621 Hanoi Highway, Thu Duc District, Ho Chi Minh City 700000, Vietnam
| | - Khanh B Vu
- Department of Chemical Engineering, School of Biotechnology, International University, Quarter 6, Linh Trung Ward, Thu Duc District, Ho Chi Minh City 700000, Vietnam.,Vietnam National University, Quarter 6, Linh Trung Ward, Thu Duc District, Ho Chi Minh City 700000, Vietnam
| | - Van V Vu
- NTT Hi-Tech Institute, Nguyen Tat Thanh University, 298-300A Nguyen Tat Thanh Street, District 4, Ho Chi Minh City 700000, Vietnam
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7
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Dade CM, Douzi B, Cambillau C, Ball G, Voulhoux R, Forest KT. The crystal structure of CbpD clarifies substrate-specificity motifs in chitin-active lytic polysaccharide monooxygenases. Acta Crystallogr D Struct Biol 2022; 78:1064-1078. [PMID: 35916229 PMCID: PMC9344471 DOI: 10.1107/s2059798322007033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Accepted: 07/08/2022] [Indexed: 11/23/2022] Open
Abstract
Pseudomonas aeruginosa secretes diverse proteins via its type 2 secretion system, including a 39 kDa chitin-binding protein, CbpD. CbpD has recently been shown to be a lytic polysaccharide monooxygenase active on chitin and to contribute substantially to virulence. To date, no structure of this virulence factor has been reported. Its first two domains are homologous to those found in the crystal structure of Vibrio cholerae GbpA, while the third domain is homologous to the NMR structure of the CBM73 domain of Cellvibrio japonicus CjLPMO10A. Here, the 3.0 Å resolution crystal structure of CbpD solved by molecular replacement is reported, which required ab initio models of each CbpD domain generated by the artificial intelligence deep-learning structure-prediction algorithm RoseTTAFold. The structure of CbpD confirms some previously reported substrate-specificity motifs among LPMOAA10s, while challenging the predictive power of others. Additionally, the structure of CbpD shows that post-translational modifications occur on the chitin-binding surface. Moreover, the structure raises interesting possibilities about how type 2 secretion-system substrates may interact with the secretion machinery and demonstrates the utility of new artificial intelligence protein structure-prediction algorithms in making challenging structural targets tractable.
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Affiliation(s)
- Christopher M. Dade
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Badreddine Douzi
- Aix-Marseille University, CNRS, IMM, LCB, Marseille, France
- Aix-Marseille University, CNRS, AFMB, Marseille, France
| | | | - Genevieve Ball
- Aix-Marseille University, CNRS, IMM, LCB, Marseille, France
| | - Romé Voulhoux
- Aix-Marseille University, CNRS, IMM, LCB, Marseille, France
| | - Katrina T. Forest
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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8
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Schröder GC, O’Dell WB, Swartz PD, Meilleur F. Preliminary results of neutron and X-ray diffraction data collection on a lytic polysaccharide monooxygenase under reduced and acidic conditions. Acta Crystallogr F Struct Biol Commun 2021; 77:128-133. [PMID: 33830078 PMCID: PMC8034432 DOI: 10.1107/s2053230x21002399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 03/02/2021] [Indexed: 11/10/2022] Open
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are copper-center enzymes that are involved in the oxidative cleavage of the glycosidic bond in crystalline cellulose and other polysaccharides. The LPMO reaction is initiated by the addition of a reductant and oxygen to ultimately form an unknown activated copper-oxygen species that is responsible for polysaccharide-substrate H-atom abstraction. Given the sensitivity of metalloproteins to radiation damage, neutron protein crystallography provides a nondestructive technique for structural characterization while also informing on the positions of H atoms. Neutron cryo-crystallography permits the trapping of catalytic intermediates, thereby providing insight into the protonation states and chemical nature of otherwise short-lived species in the reaction mechanism. To characterize the reaction-mechanism intermediates of LPMO9D from Neurospora crassa, a cryo-neutron diffraction data set was collected from an ascorbate-reduced crystal. A second neutron diffraction data set was collected at room temperature from an LPMO9D crystal exposed to low-pH conditions to probe the protonation states of ionizable groups involved in catalysis under acidic conditions.
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Affiliation(s)
- Gabriela C. Schröder
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - William B. O’Dell
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Paul D. Swartz
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Flora Meilleur
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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9
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Wang Z, Feng S, Rovira C, Wang B. How Oxygen Binding Enhances Long‐Range Electron Transfer: Lessons From Reduction of Lytic Polysaccharide Monooxygenases by Cellobiose Dehydrogenase. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202011408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Zhanfeng Wang
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry College of Chemistry and Chemical Engineering Xiamen University Xiamen 361005 China
| | - Shishi Feng
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry College of Chemistry and Chemical Engineering Xiamen University Xiamen 361005 China
| | - Carme Rovira
- Departament de Química Inorgànica i Orgànica & Institut de Química Teòrica i Computacional (IQTCUB) Universitat de Barcelona 08028 Barcelona Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA) Passeig Lluís Companys 08020 Barcelona Spain
| | - Binju Wang
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry College of Chemistry and Chemical Engineering Xiamen University Xiamen 361005 China
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10
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Theibich YA, Sauer SP, Leggio LL, Hedegård ED. Estimating the accuracy of calculated electron paramagnetic resonance hyperfine couplings for a lytic polysaccharide monooxygenase. Comput Struct Biotechnol J 2020; 19:555-567. [PMID: 33510861 PMCID: PMC7807142 DOI: 10.1016/j.csbj.2020.12.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 12/11/2020] [Accepted: 12/13/2020] [Indexed: 11/07/2022] Open
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are enzymes that bind polysaccharides followed by an (oxidative) disruption of the polysaccharide surface, thereby boosting depolymerization. The binding process between the LPMO catalytic domain and polysaccharide is key to the mechanism and establishing structure-function relationships for this binding is therefore crucial. The hyperfine coupling constants (HFCs) from EPR spectroscopy have proven useful for this purpose. Unfortunately, EPR does not provide direct structural data and therefore the experimental EPR parameters have to be supported with parameters calculated with density functional theory. Yet, calculated HFCs are extremely sensitive to the employed computational setup. Using the LPMO Ls(AA9)A catalytic domain, we here quantify the importance of several choices in the computational setup, ranging from the use of specialized basis, the underlying structures, and the employed exchange-correlation functional. We show that specialized basis sets are an absolute necessity, and also that care has to be taken in the optimization of the underlying structure: only by allowing large parts of the protein around the active site to structurally relax could we obtain results that uniformly reproduced experimental trends. We compare our results to previously published X-ray structures and experimental HFCs for Ls(AA9)A as well as to recent experimental/theoretical results for another (AA10) family of LPMOs.
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Affiliation(s)
- Yusuf A. Theibich
- Department of Chemistry, University of University, Copenhagen, Denmark
| | | | - Leila Lo Leggio
- Department of Chemistry, University of University, Copenhagen, Denmark
| | - Erik D. Hedegård
- Division of Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, SE-221 00 Lund, Sweden
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11
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Wang Z, Feng S, Rovira C, Wang B. How Oxygen Binding Enhances Long‐Range Electron Transfer: Lessons From Reduction of Lytic Polysaccharide Monooxygenases by Cellobiose Dehydrogenase. Angew Chem Int Ed Engl 2020; 60:2385-2392. [DOI: 10.1002/anie.202011408] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 10/05/2020] [Indexed: 02/02/2023]
Affiliation(s)
- Zhanfeng Wang
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry College of Chemistry and Chemical Engineering Xiamen University Xiamen 361005 China
| | - Shishi Feng
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry College of Chemistry and Chemical Engineering Xiamen University Xiamen 361005 China
| | - Carme Rovira
- Departament de Química Inorgànica i Orgànica & Institut de Química Teòrica i Computacional (IQTCUB) Universitat de Barcelona 08028 Barcelona Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA) Passeig Lluís Companys 08020 Barcelona Spain
| | - Binju Wang
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry College of Chemistry and Chemical Engineering Xiamen University Xiamen 361005 China
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12
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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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13
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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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14
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Larsson ED, Dong G, Veryazov V, Ryde U, Hedegård ED. Is density functional theory accurate for lytic polysaccharide monooxygenase enzymes? Dalton Trans 2020; 49:1501-1512. [PMID: 31922155 DOI: 10.1039/c9dt04486h] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The lytic polysaccharide monooxygenase (LPMO) enzymes boost polysaccharide depolymerization through oxidative chemistry, which has fueled the hope for more energy-efficient production of biofuel. We have recently proposed a mechanism for the oxidation of the polysaccharide substrate (E. D. Hedegård and U. Ryde, Chem. Sci., 2018, 9, 3866-3880). In this mechanism, intermediates with superoxide, oxyl, as well as hydroxyl (i.e. [CuO2]+, [CuO]+ and [CuOH]2+) cores were involved. These complexes can have both singlet and triplet spin states, and both spin-states may be important for how LPMOs function during catalytic turnover. Previous calculations on LPMOs have exclusively been based on density functional theory (DFT). However, different DFT functionals are known to display large differences for spin-state splittings in transition-metal complexes, and this has also been an issue for LPMOs. In this paper, we study the accuracy of DFT for spin-state splittings in superoxide, oxyl, and hydroxyl intermediates involved in LPMO turnover. As reference we employ multiconfigurational perturbation theory (CASPT2).
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Affiliation(s)
- Ernst D Larsson
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, SE-221 00 Lund, Sweden.
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15
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Forsberg Z, Sørlie M, Petrović D, Courtade G, Aachmann FL, Vaaje-Kolstad G, Bissaro B, Røhr ÅK, Eijsink VGH. Polysaccharide degradation by lytic polysaccharide monooxygenases. Curr Opin Struct Biol 2019; 59:54-64. [DOI: 10.1016/j.sbi.2019.02.015] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 02/22/2019] [Accepted: 02/28/2019] [Indexed: 12/22/2022]
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16
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Diaz DE, Bhadra M, Karlin KD. Dimethylanilinic N-Oxides and Their Oxygen Surrogacy Role in the Formation of a Putative High-Valent Copper-Oxygen Species. Inorg Chem 2019; 58:13746-13750. [PMID: 31580063 PMCID: PMC6896993 DOI: 10.1021/acs.inorgchem.9b02066] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reaction of p-cyano-N,N-dimethylaniline N-oxide, an O-atom donor, with different copper(I) complexes (at room temperature and in acetone) indicates the formation via O-atom transfer of a high-valent copper oxyl species, CuII-O•, a putative key intermediate in the catalytic cycle of copper-containing monooxygenases. The formation of p-cyano-N-hydroxymethyl-N-methylaniline and p-cyano-N-methylaniline as the main products of the reaction highlight the capability of this species to hydroxylate strong C-H bonds (bond dissociation energy ∼ 90 kcal/mol). A plausible mechanism for the reactivity of this catalytic system is proposed.
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Affiliation(s)
- Daniel E. Diaz
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Mayukh Bhadra
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kenneth D. Karlin
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
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17
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Wang B, Walton PH, Rovira C. Molecular Mechanisms of Oxygen Activation and Hydrogen Peroxide Formation in Lytic Polysaccharide Monooxygenases. ACS Catal 2019; 9:4958-4969. [PMID: 32051771 PMCID: PMC7007194 DOI: 10.1021/acscatal.9b00778] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 04/17/2019] [Indexed: 12/26/2022]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes for the degradation of recalcitrant polysaccharides such as chitin and cellulose. Unlike classical hydrolytic enzymes (cellulases), LPMOs catalyze the cleavage of the glycosidic bond via an oxidative mechanism using oxygen and a reductant. The full enzymatic molecular mechanisms, starting from the initial electron transfer from a reductant to oxygen activation and hydrogen peroxide formation, are not yet understood. Using quantum mechanics/molecular mechanics (QM/MM) metadynamics simulations, we have uncovered the oxygen activation mechanisms by LPMO in the presence of ascorbic acid, one of the most-used reductants in LPMOs assays. Our simulations capture the sequential formation of Cu(II)-O2 - and Cu(II)-OOH- intermediates via facile H atom abstraction from ascorbate. By investigating all the possible reaction pathways from the Cu(II)-OOH- intermediate, we ruled out Cu(II)-O• - formation via direct O-O cleavage of Cu(II)-OOH-. Meanwhile, we identified a possible pathway in which the proximal O atom of Cu(II)-OOH- abstracts a hydrogen atom from ascorbate, leading to Cu(I) and H2O2. The in-situ-generated H2O2 either converts to LPMO-Cu(II)-O• - via a homolytic reaction, or diffuses into the bulk water in an uncoupled pathway. The competition of these two pathways is strongly dependent on the binding of the carbohydrate substrate, which plays a role in barricading the in-situ-generated H2O2 molecule, preventing its diffusion from the active site into the bulk water. Based on the present results, we propose a catalytic cycle of LPMOs that is consistent with the experimental information available. In particular, it explains the enigmatic substrate dependence of the reactivity of the LPMO with H2O2.
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Affiliation(s)
- Binju Wang
- Departament de Química Inorgànica i Orgànica & IQTCUB, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
| | - Paul H. Walton
- Department of Chemistry, University of York, Heslington, YO10 5DD, United Kingdom
| | - Carme Rovira
- Departament de Química Inorgànica i Orgànica & IQTCUB, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08020 Barcelona, Spain
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18
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Hangasky JA, Detomasi TC, Marletta MA. Glycosidic Bond Hydroxylation by Polysaccharide Monooxygenases. TRENDS IN CHEMISTRY 2019. [DOI: 10.1016/j.trechm.2019.01.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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19
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Bissaro B, Várnai A, Røhr ÅK, Eijsink VGH. Oxidoreductases and Reactive Oxygen Species in Conversion of Lignocellulosic Biomass. Microbiol Mol Biol Rev 2018; 82:e00029-18. [PMID: 30257993 PMCID: PMC6298611 DOI: 10.1128/mmbr.00029-18] [Citation(s) in RCA: 157] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Biomass constitutes an appealing alternative to fossil resources for the production of materials and energy. The abundance and attractiveness of vegetal biomass come along with challenges pertaining to the intricacy of its structure, evolved during billions of years to face and resist abiotic and biotic attacks. To achieve the daunting goal of plant cell wall decomposition, microorganisms have developed many (enzymatic) strategies, from which we seek inspiration to develop biotechnological processes. A major breakthrough in the field has been the discovery of enzymes today known as lytic polysaccharide monooxygenases (LPMOs), which, by catalyzing the oxidative cleavage of recalcitrant polysaccharides, allow canonical hydrolytic enzymes to depolymerize the biomass more efficiently. Very recently, it has been shown that LPMOs are not classical monooxygenases in that they can also use hydrogen peroxide (H2O2) as an oxidant. This discovery calls for a revision of our understanding of how lignocellulolytic enzymes are connected since H2O2 is produced and used by several of them. The first part of this review is dedicated to the LPMO paradigm, describing knowns, unknowns, and uncertainties. We then present different lignocellulolytic redox systems, enzymatic or not, that depend on fluxes of reactive oxygen species (ROS). Based on an assessment of these putatively interconnected systems, we suggest that fine-tuning of H2O2 levels and proximity between sites of H2O2 production and consumption are important for fungal biomass conversion. In the last part of this review, we discuss how our evolving understanding of redox processes involved in biomass depolymerization may translate into industrial applications.
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Affiliation(s)
- Bastien Bissaro
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Aas, Norway
| | - Anikó Várnai
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Aas, Norway
| | - Åsmund K Røhr
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Aas, Norway
| | - Vincent G H Eijsink
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Aas, Norway
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20
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21
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Hangasky JA, Iavarone AT, Marletta MA. Reactivity of O 2 versus H 2O 2 with polysaccharide monooxygenases. Proc Natl Acad Sci U S A 2018; 115:4915-4920. [PMID: 29686097 PMCID: PMC5949000 DOI: 10.1073/pnas.1801153115] [Citation(s) in RCA: 130] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Enzymatic conversion of polysaccharides into lower-molecular-weight, soluble oligosaccharides is dependent on the action of hydrolytic and oxidative enzymes. Polysaccharide monooxygenases (PMOs) use an oxidative mechanism to break the glycosidic bond of polymeric carbohydrates, thereby disrupting the crystalline packing and creating new chain ends for hydrolases to depolymerize and degrade recalcitrant polysaccharides. PMOs contain a mononuclear Cu(II) center that is directly involved in C-H bond hydroxylation. Molecular oxygen was the accepted cosubstrate utilized by this family of enzymes until a recent report indicated reactivity was dependent on H2O2 Reported here is a detailed analysis of PMO reactivity with H2O2 and O2, in conjunction with high-resolution MS measurements. The cosubstrate utilized by the enzyme is dependent on the assay conditions. PMOs will directly reduce O2 in the coupled hydroxylation of substrate (monooxygenase activity) and will also utilize H2O2 (peroxygenase activity) produced from the uncoupled reduction of O2 Both cosubstrates require Cu reduction to Cu(I), but the reaction with H2O2 leads to nonspecific oxidation of the polysaccharide that is consistent with the generation of a hydroxyl radical-based mechanism in Fenton-like chemistry, while the O2 reaction leads to regioselective substrate oxidation using an enzyme-bound Cu/O2 reactive intermediate. Moreover, H2O2 does not influence the ability of secretome from Neurospora crassa to degrade Avicel, providing evidence that molecular oxygen is a physiologically relevant cosubstrate for PMOs.
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Affiliation(s)
- John A Hangasky
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720
| | - Anthony T Iavarone
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720
- Department of Chemistry, University of California, Berkeley, CA 94720
| | - Michael A Marletta
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720;
- Department of Chemistry, University of California, Berkeley, CA 94720
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
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22
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Hangasky JA, Marletta MA. A Random-Sequential Kinetic Mechanism for Polysaccharide Monooxygenases. Biochemistry 2018; 57:3191-3199. [PMID: 29683313 DOI: 10.1021/acs.biochem.8b00129] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polysaccharide monooxygenases (PMOs) are mononuclear copper enzymes that catalyze the hydroxylation of polysaccharides leading to the scission of the glycosidic bond. The mechanism, in which PMOs utilize molecular oxygen to oxidize the polysaccharide substrate, still remains largely unknown. Here, steady-state kinetics assays were used to probe the mechanism of oxygen-dependent cellohexaose oxidation catalyzed by MtPMO9E. Kinetic analysis indicated that both kcat/ KM(O2) and kcat/ KM(Glc6) were dependent on the concentration of the second substrate. Inhibition studies using carbon monoxide were also carried out. In addition, KD values for Glc6 were determined for the Cu(I) and Cu(II) forms of the enzyme. Taken together, PMOs follow a random-sequential kinetic mechanism to form a ternary ES-O2 complex. The optimal pH for MtPMO9E turnover was determined to be between pH 6.00 and pH 7.00. Furthermore, the kinetic parameters kcat, kcat/ KM(O2), and kcat/ KM(Glc6) demonstrate a decrease in PMO activity at a low pH and provide equivalent kinetic p Ka's of 5.10. This points to the protonation of a general base required for turnover. These results provide a basis for the initial chemical steps in the mechanism of PMOs.
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Affiliation(s)
- John A Hangasky
- California Institute for Quantitative Biosciences (QB3) , University of California , Berkeley , California 94720 , United States
| | - Michael A Marletta
- California Institute for Quantitative Biosciences (QB3) , University of California , Berkeley , California 94720 , United States.,Department of Chemistry , University of California , Berkeley , California 94720 , United States.,Department of Molecular and Cell Biology , University of California , Berkeley , California 94720 , United States
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23
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Hedegård ED, Ryde U. Molecular mechanism of lytic polysaccharide monooxygenases. Chem Sci 2018; 9:3866-3880. [PMID: 29780519 PMCID: PMC5935029 DOI: 10.1039/c8sc00426a] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 03/23/2018] [Indexed: 11/23/2022] Open
Abstract
The lytic polysaccharide monooxygenases (LPMOs) are copper metalloenzymes that can enhance polysaccharide depolymerization through an oxidative mechanism and hence boost generation of biofuel from e.g. cellulose. By employing density functional theory in a combination of quantum mechanics and molecular mechanics (QM/MM), we report a complete description of the molecular mechanism of LPMOs.
The lytic polysaccharide monooxygenases (LPMOs) are copper metalloenzymes that can enhance polysaccharide depolymerization through an oxidative mechanism and hence boost generation of biofuel from e.g. cellulose. By employing density functional theory in a combination of quantum mechanics and molecular mechanics (QM/MM), we report a complete description of the molecular mechanism of LPMOs. The QM/MM scheme allows us to describe all reaction steps with a detailed protein environment and we show that this is necessary. Several active species capable of abstracting a hydrogen from the substrate have been proposed previously and starting from recent crystallographic work on a substrate–LPMO complex, we investigate previously suggested paths as well as new ones. We describe the generation of the reactive intermediates, the abstraction of a hydrogen atom from the polysaccharide substrate, as well as the final recombination step in which OH is transferred back to the substrate. We show that a superoxo [CuO2]+ complex can be protonated by a nearby histidine residue (suggested by recent mutagenesis studies and crystallographic work) and, provided an electron source is available, leads to formation of an oxyl-complex after cleavage of the O–O bond and dissociation of water. The oxyl complex either reacts with the substrate or is further protonated to a hydroxyl complex. Both the oxyl and hydroxyl complexes are also readily generated from a reaction with H2O2, which was recently suggested to be the true co-substrate, rather than O2. The C–H abstraction by the oxyl and hydroxy complexes is overall favorable with activation barriers of 69 and 94 kJ mol–1, compared to the much higher barrier (156 kJ mol–1) obtained for the copper–superoxo species. We obtain good structural agreement for intermediates for which structural data are available and the estimated reaction energies agree with experimental rate constants. Thus, our suggested mechanism is the most complete to date and concur with available experimental evidence.
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Affiliation(s)
- Erik Donovan Hedegård
- Department of Theoretical Chemistry , Lund University , P. O. Box 124 , SE-221 00 , Lund , Sweden .
| | - Ulf Ryde
- Department of Theoretical Chemistry , Lund University , P. O. Box 124 , SE-221 00 , Lund , Sweden .
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24
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Meier KK, Jones SM, Kaper T, Hansson H, Koetsier MJ, Karkehabadi S, Solomon EI, Sandgren M, Kelemen B. Oxygen Activation by Cu LPMOs in Recalcitrant Carbohydrate Polysaccharide Conversion to Monomer Sugars. Chem Rev 2018; 118:2593-2635. [PMID: 29155571 PMCID: PMC5982588 DOI: 10.1021/acs.chemrev.7b00421] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Natural carbohydrate polymers such as starch, cellulose, and chitin provide renewable alternatives to fossil fuels as a source for fuels and materials. As such, there is considerable interest in their conversion for industrial purposes, which is evidenced by the established and emerging markets for products derived from these natural polymers. In many cases, this is achieved via industrial processes that use enzymes to break down carbohydrates to monomer sugars. One of the major challenges facing large-scale industrial applications utilizing natural carbohydrate polymers is rooted in the fact that naturally occurring forms of starch, cellulose, and chitin can have tightly packed organizations of polymer chains with low hydration levels, giving rise to crystalline structures that are highly recalcitrant to enzymatic degradation. The topic of this review is oxidative cleavage of carbohydrate polymers by lytic polysaccharide mono-oxygenases (LPMOs). LPMOs are copper-dependent enzymes (EC 1.14.99.53-56) that, with glycoside hydrolases, participate in the degradation of recalcitrant carbohydrate polymers. Their activity and structural underpinnings provide insights into biological mechanisms of polysaccharide degradation.
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Affiliation(s)
- Katlyn K. Meier
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Stephen M. Jones
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Thijs Kaper
- DuPont Industrial Biosciences, 925 Page Mill Road, Palo Alto, California 94304, United States
| | - Henrik Hansson
- Department of Molecular Sciences, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-750 07 Uppsala, Sweden
| | - Martijn J. Koetsier
- DuPont Industrial Biosciences, Netherlands, Nieuwe Kanaal 7-S, 6709 PA Wageningen, The Netherlands
| | - Saeid Karkehabadi
- Department of Molecular Sciences, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-750 07 Uppsala, Sweden
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Mats Sandgren
- Department of Molecular Sciences, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-750 07 Uppsala, Sweden
| | - Bradley Kelemen
- DuPont Industrial Biosciences, 925 Page Mill Road, Palo Alto, California 94304, United States
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25
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Wang B, Johnston EM, Li P, Shaik S, Davies GJ, Walton PH, Rovira C. QM/MM Studies into the H2O2-Dependent Activity of Lytic Polysaccharide Monooxygenases: Evidence for the Formation of a Caged Hydroxyl Radical Intermediate. ACS Catal 2018. [DOI: 10.1021/acscatal.7b03888] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Binju Wang
- Departament de Química Inorgànica i Orgànica (secció de Química Orgànica) & IQTCUB, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
| | | | - Pengfei Li
- Department
of Chemistry, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Department
of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel
| | - Gideon J. Davies
- York Structural
Biology Laboratory, 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 Química Inorgànica i Orgànica (secció de Química Orgànica) & IQTCUB, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08020 Barcelona, Spain
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26
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Hedegård ED, Ryde U. Targeting the reactive intermediate in polysaccharide monooxygenases. J Biol Inorg Chem 2017; 22:1029-1037. [PMID: 28698982 PMCID: PMC5613103 DOI: 10.1007/s00775-017-1480-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Accepted: 06/29/2017] [Indexed: 01/15/2023]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are copper metalloenzymes that can enhance polysaccharide depolymerization through an oxidative mechanism, making them interesting for the production of biofuel from cellulose. However, the details of this activation are unknown; in particular, the nature of the intermediate that attacks the glycoside C-H bond in the polysaccharide is not known, and a number of different species have been suggested. The homolytic bond-dissociation energy (BDE) has often been used as a descriptor for the bond-activation power, especially for inorganic model complexes. We have employed quantum-chemical cluster calculations to estimate the BDE for a number of possible LPMO intermediates to bridge the gap between model complexes and the actual LPMO active site. The calculated BDEs suggest that the reactive intermediate is either a Cu(II)-oxyl, a Cu(III)-oxyl, or a Cu(III)-hydroxide, which indicate that O-O bond breaking occurs before the C-H activation step.
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Affiliation(s)
- Erik D. Hedegård
- Department of Chemistry, Chemical Centre, Lund University, Sölvegatan 39, Lund, Sweden
| | - Ulf Ryde
- Department of Chemistry, Chemical Centre, Lund University, Sölvegatan 39, Lund, Sweden
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