Polysaccharide Monooxygenases Research Articles

Cloning of an AA13 Polysaccharide Monooxygenase Gene from Neurospora crassa into the plasmid pEX2B

Polysaccharide monooxygenases (PMOs) cleave glycoside linkages in polysaccharides, which has great potential in manufacturing biofuel from polysaccharide biomasses. Therefore, heterologous production of PMOs is required for the development of their application. We aim to clone PMO genes into the plasmid pEX2B to express PMOs in Aspergillus oryzae, a filamentous fungus widely used for industrial enzyme production.Here we cloned the NCU08746 gene, an AA13 PMO from Neurospora crassa, into pEX2B. We successfully designed primers and amplified the NCU08746 gene from the N. crassa genome. NCU08746 was then cloned into the pEX2B vector. The recombinant plasmid pEX2B-NCU08746 was subsequently transferred into A. tumefaciens AGL1 prior to being transferred into A. oryzae. This work provides the foundation for further study on PMOs expression in A. oryzae.

Cloning of AA9 Polysaccharide Monooxygenase gene AN3860 into pEX2B for expression in Aspergillus oryzae

Polysaccharide monooxygenases (PMOs) catalyze oxidative degradation of recalcitrant carbohydrate chains in cellulose, starch, and chitin. In biofuel industry, the conversion of rich lignocellulose source to fermentable sugars by hydrolytic cellulases can be synergistically boosted by cellulose-active PMOs (AA9 PMOs) found in a vast number of fungi that grow on biomass. Aspergillus nidulans, a filamentous fungus, possess a dozen of PMO-encoding genes, but only the AN3860 is expressed at a high level when cultured with wheat straw as the sole carbon source. Bioinformatic analysis indicates that AN3860 belongs to type 3 AA9 PMO subfamily that is capable of hydroxylating both C1 and C4 of the glycosidic linkages. Therefore, AN3860 may be a potential enzyme to improve cellulose hydrolysis efficiency, which has not been characterized. In this study, we describe the AN3860 cloning into Aspergillus oryzae AUT1-PlD. To facilitate the purification of AN3860, we added a CBM20 tag to its C-terminal. The recombinant vector was designed and constructed successfully. Simultaneously, we have obtained the clone of A. oryzae carrying the target gene by the ATMT method. Further expression optimization and characterization of AN3860 by both activity assays and spectroscopic techniques are underway.

Study on AA10 expression in E. coli

The GlcNAc-binding protein A (GbpA) has been known as a virulent factor of Vibrio vulnificus pathogen. Domain 1 of GbpA adhesion takes responsibility of binding both human intestine and the chitinous surface. The domain 1 structure is similar to a polysaccharide monooxygenase (PMO) AA10-type (PMO), which catalyzed oxidation toward the recalcitrant chitin polymer. The role of the VvPMO10 module in catalytic functions has not been fulfilled characterized. To aim of the VvPMO10 study, this protein was cloned to the pET22b system and transformed into the E. coli BL21 (DE3) strain. The recombinant enzyme was expressed at 37 0C with IPTG induced. Total protein was checked by SDS-PAGE method and stained using Coomassie blue solution. The target band showed a band of 20 kDa as expectation. Thus, the heterologous protein was expressed successfully in E. coli BL21 (DE3) strain and becomes the materials for future study.

CARBOHYDRASES – 50 YEARS OF RESEARCH AT THE DEPARTMENT OF CHEMICAL ENZYMOLOGY OF LOMONOSOV MOSCOW STATE UNIVERSITY, HISTORY AND PROSPECTS

The review describes the history of the development of research on carbohydrasеs conducted at the Department of Chemical Enzymology from the mid-1970s to the present. The results concerning the study of the mechanism and kinetics of the processes of enzymatic conversion of cellulose and renewable plant raw materials under the action of a multi-enzyme cellulases complexes; the role of individual components of these complexes - basic (endoglucanases and cellobiohydrolases) and auxiliary enzymes (polysaccharide monooxygenase, β-glucosidase, xylanase) and their synergistic interaction. The features of using reactors of various designs for bioconversion of plant raw materials are described: periodic type, continuous column type, reactor for hydrolysis in a constant electric field, reactor with intensive mixing by ferromagnetic particles in magnetic field. The possibilities of increasing the reactivity of plant raw materials using various pretreatment methods, as well as the influence of the structural and physico-chemical properties of cellulose on the efficiency of its enzymatic conversion are discussed. Data on the creation of highly active strains of microscopic fungi-producers of cellulases and other carbohydrases using methods of induced mutagenesis - Trichoderma (Hypocrea), Penicillium (Talaromyces), Aspergillus, Chrysosporium (Myceliophtora) spp., as well as data on the composition of the enzyme complexes produced by them and the properties of the enzymes forming them are presented. It describes the creation of expression systems based on P. canescens and P. verruculosum and the production of recombinant producer strains with their help, which made it possible to obtain enzyme preparations (EP) that ensure high efficiency of bioconversion processes of plant raw materials, as well as to create producers of a wide range of carbohydrases for practical use in various fields of industry and agriculture. A number of industrially important EP obtained using the P. verruculosum expression system are currently being produced at the Agroferment LLC plant.

Heterologous expression and characterization of a MoAA16 polysaccharide monooxygenase from the rice blast fungus Magnaporthe oryzae

BackgroundCellulose is an organic carbon source that can be used as a sustainable alternative for energy, materials, and chemicals. However, the substantial challenge of converting it into soluble sugars remains a major obstacle in its use as a biofuel and chemical feedstock. A new class of enzymes knowns as copper-dependent polysaccharide monooxygenases (PMOs) or lytic polysaccharide monooxygenases (LPMOs) can break down polysaccharides such as cellulose, chitin, and starch through oxidation. This process enhances the efficiency of cellulose degradation by cellulase. ResultsThe genome of the fungus Magnaporthe oryzae, the causal agent of rice blast disease, contains the MGG_00245 gene, which encodes a putative PMO referred to as MoAA16. MoAA16 has been found to be highly expressed in planta during the early stages of fungal infection. The gene was optimized for heterologous expression in Pichia pastoris, and its oxidative cleavage activity on cellulose was characterized by analyzing soluble oligosaccharide products using highperformance anion exchange chromatography (HPAEC-PAD). The reaction catalyzed by MoAA16 requires 2 electrons from an electron donor, such as ascorbic acid, and aerobic conditions. It primarily produces Glc1 to Glc4 oligosaccharides, as well as oxidized cellobionic and cellotrionic acids. MoAA16 has been observed to enhance cellulase hydrolysis on phosphoric acid swollen cellulose (PASC) substrate, resulting in the production of more monosaccharide products. ConclusionsOur findings reveal the successful heterologous expression of MoAA16 in P. pastoris and its cellulose-active PMO properties. These results highlight the potential of MoAA16 as a promising candidate for applications in biofuel production and chemical synthesis.How to cite: Nguyen HM, Le LQ, Sella L, et al. Heterologous expression and characterization of a MoAA16 polysaccharide monooxygenase from the rice blast fungus Magnaporthe oryzae. Electron J Biotechnol 2023. https://doi.org/10.1016/j.ejbt.2023.06.002.

Isolation and identification of Vibrio spp. with potential ability to produce polysaccharide monooxygenase from diseased Penaeus monodon

Polysaccharide monooxygenases (PMOs) and Glycoside Hydrolases (GH) play a crucial role in breaking down chitin and cellulose. Research on PMOs has mainly focused on their role in the production of bioethanol from biomass. Still, the potential of PMOs as virulence factors in microorganisms is not been fully studied. Some pathogenic bacteria secrete PMOs, which have been identified as virulence factors. The ability of Vibrio species to metabolize chitin is well-known, but the question of which Vibrio species contains the PMO gene remains unanswered. Materials and methods: Black tiger shrimp Penaeus monodon was collected from a culture pond in Long An, Vietnam. Thiosulfate-citrate-bile salts-sucrose and CHROMagar Vibrio agar were used to isolate, Vibrio bacteria from the shrimp samples. Mixed bases primers were designed to detect PMOs gene from Vibrio strains. Results: Total of 35 different strains of bacteria were isolated from the guts and pancreas of the shrimp sample. Based on biochemical tests, there were a total of 20 different Vibrio strains identified among 35 isolated strains. The PCR results showed that six isolates could have the PMOs gene. The partial 16S rDNA fragments of six isolate Vibrio strains were sequenced. Comparing 16S rDNA sequences with sequences available in NCBI databases revealed that all the sequences are Vibrio spp. 16S rDNA sequences.

Characterization of a unique polysaccharide monooxygenase from the plant pathogen Magnaporthe oryzae

Blast disease in cereal plants is caused by the fungus Magnaporthe oryzae and accounts for a significant loss in food crops. At the outset of infection, expression of a putative polysaccharide monooxygenase (MoPMO9A) is increased. MoPMO9A contains a catalytic domain predicted to act on cellulose and a carbohydrate-binding domain that binds chitin. A sequence similarity network of the MoPMO9A family AA9 showed that 220 of the 223 sequences in the MoPMO9A-containing cluster of sequences have a conserved unannotated region with no assigned function. Expression and purification of the full length and two MoPMO9A truncations, one containing the catalytic domain and the domain of unknown function (DUF) and one with only the catalytic domain, were carried out. In contrast to other AA9 polysaccharide monooxygenases (PMOs), MoPMO9A is not active on cellulose but showed activity on cereal-derived mixed (1→3, 1→4)-β-D-glucans (MBG). Moreover, the DUF is required for activity. MoPMO9A exhibits activity consistent with C4 oxidation of the polysaccharide and can utilize either oxygen or hydrogen peroxide as a cosubstrate. It contains a predicted 3-dimensional fold characteristic of other PMOs. The DUF is predicted to form a coiled-coil with six absolutely conserved cysteines acting as a zipper between the two α-helices. MoPMO9A substrate specificity and domain architecture are different from previously characterized AA9 PMOs. The results, including a gene ontology analysis, support a role for MoPMO9A in MBG degradation during plant infection. Consistent with this analysis, deletion of MoPMO9A results in reduced pathogenicity.

Distal Hydrophobic Loop Modulates the Copper Active Site and Reaction of AA13 Polysaccharide Monooxygenases.

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.

A New Enzyme Preparation Containing Polysaccharide Monooxygenase and β-Glucosidase—Synergistic Additives to Cellulases

A New Enzyme Preparation Containing Polysaccharide Monooxygenase and β-Glucosidase—Synergistic Additives to Cellulases

OPTIMIZATION OF THE PROCESS OF SACCHARIFICATION OF HARDWOOD CELLULOSE UNDER THE ACTION OF HYDROLASES AND OXYGENASES

A complex of enzymes has been selected for the exhaustive enzymatic conversion of semi-bleached sulfate hardwood pulp to monosaccharides, carried out in the substrate concentration range from 100 to 300 g/l. The role of cellulases, xylanase, β-glucosidase and polysaccharide monooxygenase in the intensification of the process is shown.

Activity and substrate specificity of lytic polysaccharide monooxygenases: An ATR FTIR-based sensitive assay tested on a novel species from Pseudomonas putida.

Pseudomonas putida W619 is a soil Gram-negative bacterium commonly used in environmental studies thanks to its ability in degrading many aromatic compounds. Its genome contains several putative carbohydrate-active enzymes such as glycoside hydrolases and lytic polysaccharide monooxygenases (PMOs). In this study, we have heterologously produced in Escherichia coli and characterized a new enzyme belonging to the AA10 family, named PpAA10 (Uniprot: B1J2U9), which contains a chitin-binding type-4 module and showed activity toward β-chitin. The active form of the enzyme was produced in E. coli exploiting the addition of a cleavable N-terminal His tag which ensured the presence of the copper-coordinating His as the first residue. Electron paramagnetic resonance spectroscopy showed signal signatures similar to those observed for the copper-binding site of chitin-cleaving PMOs. The protein was used to develop a versatile, highly sensitive, cost-effective and easy-to-apply method to detect PMO's activity exploiting attenuated total reflection-Fourier transform infrared spectroscopy and able to easily discriminate between different substrates.

Study on AA10 expression in E. coli

The GlcNAc-binding protein A (GbpA) has been known as a virulent factor of Vibrio vulnificus pathogen. Domain 1 of GbpA adhesion takes responsibility of binding both human intestine and the chitinous surface. The domain 1 structure is similar to a polysaccharide monooxygenase (PMO) AA10-type (PMO), which catalyzed oxidation toward the recalcitrant chitin polymer. The role of the VvPMO10 module in catalytic functions has not been fulfilled characterized. To aim of the VvPMO10 study, this protein was cloned to the pET22b system and transformed into the E. coli BL21 (DE3) strain. The recombinant enzyme was expressed at 37 0C with IPTG induced. Total protein was checked by SDS-PAGE method and stained using Coomassie blue solution. The target band showed a band of 20 kDa as expectation. Thus, the heterologous protein was expressed successfully in E. coli BL21 (DE3) strain and becomes the materials for future study.

Biologically active secondary metabolites and biotechnological applications of species of the family Chaetomiaceae (Sordariales): an updated review from 2016 to 2021

Fungi are eukaryotic organisms that have the ability to synthesize an enormous number of metabolites with a vast diversity of chemical structures and bioactivities. Chaetomiaceae species are a wealthy source of enzymes with diverse biotechnological and industrial applications such as PMO (polysaccharide monooxygenase), L-methioninase, β-1,3-glucanase, laccase, dextranase, lipolytic, pectinolytic, amylolytic, chitinolytic, and proteolytic enzymes. Different classes of secondary metabolites have been reported from this family are derived from various biosynthetic pathways such as alkaloids, polyketides, peptides, terpenes, and polyketide-amino acid hybrid secondary metabolites. These metabolites have attracted research interest due to their fascinating structural frameworks and bioactivities. Therefore, these compounds can be taken into account as candidates for the development of effective and novel lead compounds for medicine, as well as for plant protection. The current review represents the relevant information for Chaetomiaceae species, in particular, its new and first reported secondary metabolites and their pharmacological activities, as well as the biotechnological applications published from 2016 until the beginning of 2021.

Cloning of an AA13 Polysaccharide Monooxygenase Gene from Neurospora crassa into the plasmid pEX2B

Polysaccharide monooxygenases (PMOs) cleave glycoside linkages in polysaccharides, which has great potential in manufacturing biofuel from polysaccharide biomasses. Therefore, heterologous production of PMOs is required for the development of their application. We aim to clone PMO genes into the plasmid pEX2B to express PMOs in Aspergillus oryzae, a filamentous fungus widely used for industrial enzyme production.Here we cloned the NCU08746 gene, an AA13 PMO from Neurospora crassa, into pEX2B. We successfully designed primers and amplified the NCU08746 gene from the N. crassa genome. NCU08746 was then cloned into the pEX2B vector. The recombinant plasmid pEX2B-NCU08746 was subsequently transferred into A. tumefaciens AGL1 prior to being transferred into A. oryzae. This work provides the foundation for further study on PMOs expression in A. oryzae.

Cloning of AA9 Polysaccharide Monooxygenase gene AN3860 into pEX2B for expression in Aspergillus oryzae

Polysaccharide monooxygenases (PMOs) catalyze oxidative degradation of recalcitrant carbohydrate chains in cellulose, starch, and chitin. In biofuel industry, the conversion of rich lignocellulose source to fermentable sugars by hydrolytic cellulases can be synergistically boosted by cellulose-active PMOs (AA9 PMOs) found in a vast number of fungi that grow on biomass. Aspergillus nidulans, a filamentous fungus, possess a dozen of PMO-encoding genes, but only the AN3860 is expressed at a high level when cultured with wheat straw as the sole carbon source. Bioinformatic analysis indicates that AN3860 belongs to type 3 AA9 PMO subfamily that is capable of hydroxylating both C1 and C4 of the glycosidic linkages. Therefore, AN3860 may be a potential enzyme to improve cellulose hydrolysis efficiency, which has not been characterized. In this study, we describe the AN3860 cloning into Aspergillus oryzae AUT1-PlD. To facilitate the purification of AN3860, we added a CBM20 tag to its C-terminal. The recombinant vector was designed and constructed successfully. Simultaneously, we have obtained the clone of A. oryzae carrying the target gene by the ATMT method. Further expression optimization and characterization of AN3860 by both activity assays and spectroscopic techniques are underway.

Fine Tuning of the Copper Active Site in Polysaccharide Monooxygenases.

Type 2 copper active sites, one of the several important copper active sites in biology, were recently found in the novel superfamily of polysaccharide monooxygenases (PMOs) that cleave recalcitrant polysaccharides via an unprecedented oxidative mechanism. The copper center in PMOs is ligated by the bidentate N-terminal histidine residue and another conserved histidine residue, forming a unique T-shaped core termed as Histidine brace. This core serves as the foundation for diverse structures and electronic properties among PMO families and subfamilies. Understanding of the copper active site in PMOs is limited to the static solid structures obtained with X-ray diffraction (XRD), whereas in several families, the copper center exists as a mixture of species in solution as indicated by electron paramagnetic resonance (EPR) spectroscopy. To obtain further details on the copper active sites in PMOs, we carried out density functional theory calculations and molecular dynamics simulations on MtPMO3* that were previously studied with XRD, EPR, mutagenesis, and activity assays. The results reveal the fine-tuning of the binding of the distal ligands by both proximal and distal H-bond-forming residues. Q167 forms H bonds with the proximal OTyr ligand of Y167 and the equatorial aqueous ligand (Oeq). T74 forms a H bond with the distal aqueous ligand (Odis). Removing these H bonds by mutating Q167 or T74 to alanine results in great fluctuations of the axial ligands. Strengthening the proximal H bonds by mutating Q167 to glutamate confines Y167 to the copper centers. In all mutants, the residence time of Odis is significantly reduced. Q167A, Q167E, and T74A mutants were previously shown to have a significantly reduced activity. Our results indicate that well-tuned H bonds are required for the activity of PMOs.

Allorecognition upon Fungal Cell-Cell Contact Determines Social Cooperation and Impacts the Acquisition of Multicellularity.

Somatic cell fusion and conspecific cooperation are crucial social traits for microbial unicellular-to-multicellular transitions, colony expansion, and substrate foraging but are also associated with risks of parasitism. We identified a cell wall remodeling (cwr) checkpoint that acts upon cell contact to assess genetic compatibility and regulate cell wall dissolution during somatic cell fusion in a wild population of the filamentous fungus Neurospora crassa. Non-allelic interactions between two linked loci, cwr-1 and cwr-2, were necessary and sufficient to block cell fusion: cwr-1 encodes a polysaccharide monooxygenase (PMO), a class of enzymes associated with extracellular degradative capacities, and cwr-2 encodes a predicted transmembrane protein. Mutations of sites in CWR-1 essential for PMO catalytic activity abolished the block in cell fusion between formerly incompatible strains. In Neurospora, alleles cwr-1 and cwr-2 were highly polymorphic, fell into distinct haplogroups, and showed trans-species polymorphisms. Distinct haplogroups and trans-species polymorphisms at cwr-1 and cwr-2 were also identified in the distantly related genus Fusarium, suggesting convergent evolution. Proteins involved in chemotropic processes showed extended localization at contact sites, suggesting that cwr regulates the transition between chemotropic growth and cell wall dissolution. Our work revealed an allorecognition surveillance system based on kind discrimination that inhibits cooperative behavior in fungi by blocking cell fusion upon contact, contributing to fungal immunity by preventing formation of chimeras between genetically non-identical colonies.

Solution structure of the reduced active site of a starch-active polysaccharide monooxygenase from Neurospora crassa

X-ray absorption spectroscopy (XAS) was utilized to gain insights into the structure and electronic properties of the reduced copper active site in NCU08746, a polysaccharide monooxygenase (PMO) from Neurospora crassa that activates O2 to cleave glycosidic linkages in starch. The reaction of NCU08746 likely starts with binding of O2 to the copper(I) center. However, the solution structure of the reduced active site in NCU08746 has not been properly elucidated. In this study, we prepared Cu(I)-NCU08746 in solution, which was snap-frozen to preserve the solution structure of the copper(I) active site prior to XAS analysis. Results show that the copper(I) center in Cu(I)-NCU08746 exhibits a 4-coordinate geometry, which is different from the 3-coordinate geometry observed for some other PMOs. This difference likely arises from the coordination of the active site tyrosine residue and could contribute to the difference in activity between NCU08746 and other PMOs.

Structural studies of the unusual metal-ion site of the GH124 endoglucanase from Ruminiclostridium thermocellum.

The recent discovery of `lytic' polysaccharide monooxygenases, copper-dependent enzymes for biomass degradation, has provided new impetus for the analysis of unusual metal-ion sites in carbohydrate-active enzymes. In this context, the CAZY family GH124 endoglucanase from Ruminiclostridium thermocellum contains an unusual metal-ion site, which was originally modelled as a Ca2+ site but features aspartic acid, asparagine and two histidine imidazoles as coordinating residues, which are more consistent with a transition-metal binding environment. It was sought to analyse whether the GH124 metal-ion site might accommodate other metals. It is demonstrated through thermal unfolding experiments that this metal-ion site can accommodate a range of transition metals (Fe2+, Cu2+, Mn2+ and Ni2+), whilst the three-dimensional structure and mass spectrometry show that one of the histidines is partially covalently modified and is present as a 2-oxohistidine residue; a feature that is rarely observed but that is believed to be involved in an `off-switch' to transition-metal binding. Atomic resolution (<1.1 Å) complexes define the metal-ion site and also reveal the binding of an unusual fructosylated oligosaccharide, which was presumably present as a contaminant in the cellohexaose used for crystallization. Although it has not been possible to detect a biological role for the unusual metal-ion site, this work highlights the need to study some of the many metal-ion sites in carbohydrate-active enzymes that have long been overlooked or previously mis-assigned.

A Random-Sequential Kinetic Mechanism for Polysaccharide Monooxygenases.

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.