| 1. |
- Charavgi, Maria-Despoina, et al.
(författare)
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The structure of a novel glucuronoyl esterase from Myceliophthora thermophila gives new insights into its role as a potential biocatalyst
- 2013
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Ingår i: Acta Crystallographica Section D. - 0907-4449 .- 1399-0047. ; 69:1, s. 63-73
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Tidskriftsartikel (refereegranskat)abstract
- The increasing demand for the development of efficient biocatalysts is a consequence of their broad industrial applications. Typical difficulties that are encountered during their exploitation in a variety of processes are interconnected with factors such as temperature, pH, product inhibitors etc. To eliminate these, research has been directed towards the identification of new enzymes that would comply with the required standards. To this end, the recently discovered glucuronoyl esterases (GEs) are an enigmatic family within the carbohydrate esterase (CE) family. Structures of the thermophilic StGE2 esterase from Myceliophthora thermophila (synonym Sporotrichum thermophile), a member of the CE15 family, and its S213A mutant were determined at 1.55 and 1.9 Å resolution, respectively. The first crystal structure of the S213A mutant in complex with a substrate analogue, methyl 4-O-methyl-[beta]-D-glucopyranuronate, was determined at 2.35 Å resolution. All of the three-dimensional protein structures have an [alpha]/[beta]-hydrolase fold with a three-layer [alpha][beta][alpha]-sandwich architecture and a Rossmann topology and comprise one molecule per asymmetric unit. These are the first crystal structures of a thermophilic GE both in an unliganded form and bound to a substrate analogue, thus unravelling the organization of the catalytic triad residues and their neighbours lining the active site. The knowledge derived offers novel insights into the key structural elements that drive the hydrolysis of glucuronic acid esters.
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| 2. |
- Dimarogona, Maria, et al.
(författare)
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Structural and functional studies of a Fusarium oxysporum cutinase with polyethylene terephthalate modification potential
- 2015
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Ingår i: Biochimica et Biophysica Acta - General Subjects. - : Elsevier BV. - 0304-4165 .- 1872-8006. ; 1850:11, s. 2308-2317
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundCutinases are serine hydrolases that degrade cutin, a polyester of fatty acids that is the main component of plant cuticle. These biocatalysts have recently attracted increased biotechnological interest due to their potential to modify and degrade polyethylene terephthalate (PET), as well as other synthetic polymers.MethodsA cutinase from the mesophilic fungus Fusarium oxysporum, named FoCut5a, was expressed either in the cytoplasm or periplasm of Escherichia coli BL21. Its X-ray structure was determined to 1.9 Å resolution using molecular replacement. The activity of the recombinant enzyme was tested on a variety of synthetic esters and polyester analogues.ResultsThe highest production of recombinant FoCut5a was achieved using periplasmic expression at 16οC. Its crystal structure is highly similar to previously determined Fusarium solani cutinase structure. However, a more detailed comparison of the surface properties and amino acid interactions revealed differences with potential impact on the biochemical properties of the two enzymes. FoCut5a showed maximum activity at 40οC and pH 8.0, while it was active on three p-nitrophenyl synthetic esters of aliphatic acids (C2, C4, C12), with the highest catalytic efficiency for the hydrolysis of the butyl ester. The recombinant cutinase was also found capable of hydrolyzing PET model substrates and synthetic polymers.ConclusionsThe first reported expression and crystal structure determination of a functional cutinase from the mesophilic fungus F. oxysporum with potential application in surface modification of PET synthetic polymers.General significanceFoCut5a could be used as a biocatalyst in industrial applications for the environmentally-friendly treatment of synthetic polymers.
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| 3. |
- Topakas, Evangelos, et al.
(författare)
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Expression, characterization and structural modelling of a feruloyl esterase from the thermophilic fungus Myceliophthora thermophila
- 2012
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 94:2, s. 399-411
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Tidskriftsartikel (refereegranskat)abstract
- A ferulic acid esterase (FAE) from the thermophilic fungus Myceliophthora thermophila (synonym Sporotrichum thermophile), belonging to the carbohydrate esterase family 1 (CE-1), was functionally expressed in methylotrophic yeast Pichia pastoris. The putative FAE from the genomic DNA was successfully cloned in P. pastoris X-33 to confirm that the enzyme exhibits FAE activity. The recombinant FAE was purified to its homogeneity (39 kDa) and subsequently characterized using a series of model substrates including methyl esters of hydroxycinnamates, alkyl ferulates and monoferuloylated 4-nitrophenyl glycosides. The substrate specificity profiling reveals that the enzyme shows a preference for the hydrolysis of methyl caffeate and p-coumarate and a strong preference for the hydrolysis of n-butyl and iso-butyl ferulate. The enzyme was active on substrates containing ferulic acid ester linked to the C-5 and C-2 linkages of arabinofuranose, whilst it was found capable of de-esterifying acetylated glucuronoxylans. Ferulic acid (FA) was efficiently released from destarched wheat bran when the esterase was incubated together with an M3 xylanase from Trichoderma longibrachiatum (a maximum of 41% total FA released after 1 h incubation). Prediction of the secondary structure of MtFae1a was performed in the PSIPRED server whilst modelling the 3D structure was accomplished by the use of the HH 3D structure prediction server.
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| 4. |
- Topakas, Evangelos, et al.
(författare)
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Functional expression of a thermophilic glucuronoyl esterase from Sporotrichum thermophile : identification of the nucleophilic serine
- 2010
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 87:5, s. 1765-1772
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Tidskriftsartikel (refereegranskat)abstract
- A glucuronoyl esterase (GE) from the thermophilic fungus Sporotrichum thermophile, belonging to the carbohydrate esterase family 15 (CE-15), was functionally expressed in the methylotrophic yeast Pichia pastoris. The putative GE gene ge2 from the genomic DNA was successfully cloned in frame with the sequence for the Saccharomyces cerevisiae α-factor secretion signal under the transcriptional control of the alcohol oxidase (AOX1) promoter and integrated in P. pastoris X-33 to confirm that the encoded enzyme StGE2 exhibits esterase activity. The enzyme was active on substrates containing glucuronic acid methyl ester, showing optimal activity at pH 7.0 and 55°C. The esterase displayed broad pH range stability between 4–10 and temperature stability up to 50°C, rendering StGE2 a strong candidate for future biotechnological applications that require robust biocatalysts. ClustalW alignment of StGE2 with characterized GEs and selected homologous sequences, members of CE-15 family, revealed a novel consensus sequence G-C-S-R-X-G that features the characteristic serine residue involved in the generally conserved catalytic mechanism of the esterase family. The putative serine has been mutated, and the corresponding enzyme has been expressed in P. pastoris to prove that the candidate nucleophilic residue is responsible for catalyzing the enzymatic reaction.
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| 5. |
- Borisova, Anna, et al.
(författare)
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Structural and Functional Characterization of a Lytic Polysaccharide Monooxygenase with Broad Substrate Specificity
- 2015
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 290, s. 22955-22969
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Tidskriftsartikel (refereegranskat)abstract
- The recently discovered lytic polysaccharide monooxygenases (LPMOs) carry out oxidative cleavage of polysaccharides and are of major importance for efficient processing of biomass. NcLPMO9C from Neurospora crassa acts both on cellulose and on non-cellulose beta-glucans, including cellodextrins and xyloglucan. The crystal structure of the catalytic domain of NcLPMO9C revealed an extended, highly polar substrate-binding surface well suited to interact with a variety of sugar substrates. The ability of NcLPMO9C to act on soluble substrates was exploited to study enzyme-substrate interactions. EPR studies demonstrated that the Cu2+-center environment is altered upon substrate binding, whereas isothermal titration calorimetry studies revealed binding affinities in the low micromolar range for polymeric substrates that are due in part to the presence of a carbohydrate-binding module (CBM1). Importantly, the novel structure of NcLPMO9Cenabled a comparative study, revealing that the oxidative regioselectivity of LPMO9s (C1, C4, or both) correlates with distinct structural features of the copper coordination sphere. In strictly C1-oxidizing LPMO9s, access to the solvent-facing axial coordination position is restricted by a conserved tyrosine residue, whereas access to this same position seems unrestricted in C4-oxidizing LPMO9s. LPMO9s known to produce a mixture of C1- and C4- oxidized products show an intermediate situation.
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| 6. |
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| 7. |
- Dimarogona, Maria, et al.
(författare)
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Cellulose degradation by oxidative enzymes
- 2012
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Ingår i: Computational and Structural Biotechnology Journal. - : Elsevier BV. - 2001-0370. ; 2:3
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Tidskriftsartikel (refereegranskat)abstract
- Enzymatic degradation of plant biomass has attracted intensive research interest for the production of economically viable biofuels. Here we present an overview of the recent findings on biocatalysts implicated in the oxidative cleavage of cellulose, including polysaccharide monooxygenases (PMOs or LPMOs which stands for lytic PMOs), cellobiose dehydrogenases (CDHs) and members of carbohydrate-binding module family 33 (CBM33). PMOs, a novel class of enzymes previously termed GH61s, boost the efficiency of common cellulases resulting in increased hydrolysis yields while lowering the protein loading needed. They act on the crystalline part of cellulose by generating oxidized and non-oxidized chain ends. An external electron donor is required for boosting the activity of PMOs. We discuss recent findings concerning their mechanism of action and identify issues and questions to be addressed in the future.
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| 8. |
- Dimarogona, Maria, et al.
(författare)
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Comparison of three seemingly similar lytic polysaccharide monooxygenases from Neurospora crassa suggests different roles in plant biomass degradation
- 2019
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 294, s. 15068-15081
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Tidskriftsartikel (refereegranskat)abstract
- Many fungi produce multiple lytic polysaccharide monooxygenases (LPMOs) with seemingly similar functions, but the biological reason for this multiplicity remains unknown. To address this question, here we carried out comparative structural and functional characterizations of three cellulose-active C4-oxidizing family AA9 LPMOs from the fungus Neurospora crassa, NcLPMO9A (NCU02240), NcLPMO9C (NCU02916), and NcLPMO9D (NCU01050). We solved the three-dimensional structure of copper-bound NcLPMO9A at 1.6-? resolution and found that NcLPMO9A and NcLPMO9C, containing a CBM1 carbohydrate-binding module, bind cellulose more strongly and were less susceptible to inactivation than NcLPMO9D, which lacks a CBM. All three LPMOs were active on tamarind xyloglucan and konjac glucomannan, generating similar products but clearly differing in activity levels. Importantly, in some cases, the addition of phosphoric acid?swollen cellulose (PASC) had a major effect on activity: NcLPMO9A was active on xyloglucan only in the presence of PASC, and PASC enhanced NcLPMO9D activity on glucomannan. Interestingly, the three enzymes also exhibited large differences in their interactions with enzymatic electron donors, which could reflect that they are optimized to act with different reducing partners. All three enzymes efficiently used H2O2 as a cosubstrate, yielding product profiles identical to those obtained in O-2-driven reactions with PASC, xyloglucan, or glucomannan. Our results indicate that seemingly similar LPMOs act preferentially on different types of copolymeric substructures in the plant cell wall, possibly because these LPMOs are functionally adapted to distinct niches differing in the types of available reductants.
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| 9. |
- Dimarogona, Maria, et al.
(författare)
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Interactions of a fungal lytic polysaccharide monooxygenase with beta-glucan substrates and cellobiose dehydrogenase
- 2016
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 113, s. 5922-5927
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Tidskriftsartikel (refereegranskat)abstract
- Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that catalyze oxidative cleavage of glycosidic bonds using molecular oxygen and an external electron donor. We have used NMR and isothermal titration calorimetry (ITC) to study the interactions of a broad-specificity fungal LPMO, NcLPMO9C, with various substrates and with cellobiose dehydrogenase (CDH), a known natural supplier of electrons. The NMR studies revealed interactions with cellohexaose that center around the copper site. NMR studies with xyloglucans, i. e., branched beta-glucans, showed an extended binding surface compared with cellohexaose, whereas ITC experiments showed slightly higher affinity and a different thermodynamic signature of binding. The ITC data also showed that although the copper ion alone hardly contributes to affinity, substrate binding is enhanced for metal-loaded enzymes that are supplied with cyanide, a mimic of O-2(-). Studies with CDH and its isolated heme b cytochrome domain unambiguously showed that the cytochrome domain of CDH interacts with the copper site of the LPMO and that substrate binding precludes interaction with CDH. Apart from providing insights into enzyme-substrate interactions in LPMOs, the present observations shed new light on possible mechanisms for electron supply during LPMO action.
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| 10. |
- Dimarogona, Maria, et al.
(författare)
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Recalcitrant polysaccharide degradation by novel oxidative biocatalysts
- 2013
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 97:19, s. 8455-8465
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Tidskriftsartikel (refereegranskat)abstract
- The classical hydrolytic mechanism for the degradation of plant polysaccharides by saprophytic microorganisms has been reconsidered after the recent landmark discovery of a new class of oxidases termed lytic polysaccharide monooxygenases (LPMOs). LPMOs are of increased biotechnological interest due to their implication in lignocellulosic biomass decomposition for the production of biofuels and high-value chemicals. They act on recalcitrant polysaccharides by a combination of hydrolytic and oxidative function, generating oxidized and non-oxidized chain ends. They are copper-dependent and require molecular oxygen and an external electron donor for their proper function. In this review, we present the recent findings concerning the mechanism of action of these oxidative enzymes and identify issues and questions to be addressed in the future
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