Microbial β-etherases and glutathione lyases for lignin valorisation in biorefineries: current state and future perspectives

Husarcíková, Jana; Voß, Hauke; Marı́a, Pablo Domı́nguez de; Schallmey, Anett

doi:10.1007/s00253-018-9040-3

Cited by 15 publications

(20 citation statements)

References 54 publications

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“…Similar pathways were also described for some other bacteria of the order Sphingomonadales (20). Even though C␣ dehydrogenases, ␤-etherases, and glutathione lyases are intracellular enzymes and, hence, likely act on soluble lignin degradation products in nature (12), their potential for lignin polymer degradation has been demonstrated in several studies (8,10,11). When applying this enzymatic pathway for lignin depolymerization, aromatic monomers such as guaiacyl hydroxypropanone (GHP) and syringyl hydroxypropanone (SHP) could be released rather selectively (10,11).…”

supporting

confidence: 62%

“…S2). Optima in the alkaline pH range have been reported for all previously known ␤-etherases as well, and they are very likely caused by the pK a of the glutathione thiol (reported pK a of 9.65 for free GSH) (9,12,20). Hence, a high pH facilitates deprotonation of the GSH thiol, which is a prerequisite for nucleophilic attack of the ether substrate.…”

Section: Resultsmentioning

confidence: 92%

“…On the other hand, enzymes such as peroxidases, laccases, and ␤-etherases are described to depolymerize lignin in nature (7). Among these, bacterial ␤-etherases have been shown in previous studies to exhibit high activities and absolute selectivity for cleavage of ␤-O-4-aryl ether bonds present in various lignin model substrates as well as lignin polymers (8)(9)(10)(11)(12). Hence, these enzymes are highly interesting for application in lignin valorization.…”

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confidence: 99%

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Database Mining for Novel Bacterial β-Etherases, Glutathione-Dependent Lignin-Degrading Enzymes

Voß

Heck

Schallmey

et al. 2020

Appl Environ Microbiol

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Lignin is the most abundant aromatic polymer in nature and a promising renewable source for the provision of aromatic platform chemicals and biofuels. β-Etherases are enzymes with a promising potential for application in lignin depolymerization due to their selectivity in the cleavage of β-O-4 aryl ether bonds. However, only a very limited number of these enzymes have been described and characterized so far. Using peptide pattern recognition (PPR) as well as phylogenetic analyses, 96 putatively novel β-etherases have been identified, some even originating from bacteria outside the order Sphingomonadales. A set of 13 diverse enzymes was selected for biochemical characterization, and β-etherase activity was confirmed for all of them. Some enzymes displayed up to 3-fold higher activity than previously known β-etherases. Moreover, conserved sequence motifs specific for either LigE- or LigF-type enzymes were deduced from multiple-sequence alignments and the PPR-derived peptides. In combination with structural information available for the β-etherases LigE and LigF, insight into the potential structural and/or functional role of conserved residues within these sequence motifs is provided. Phylogenetic analyses further suggest the presence of additional bacterial enzymes with potential β-etherase activity outside the classical LigE- and LigF-type enzymes as well as the recently described heterodimeric β-etherases. IMPORTANCE The use of biomass as a renewable source and replacement for crude oil for the provision of chemicals and fuels is of major importance for current and future societies. Lignin, the most abundant aromatic polymer in nature, holds promise as a renewable starting material for the generation of required aromatic structures. However, a controlled and selective lignin depolymerization to yield desired aromatic structures is a very challenging task. In this regard, bacterial β-etherases are especially interesting, as they are able to cleave the most abundant bond type in lignin with high selectivity. With this study, we significantly expanded the toolbox of available β-etherases for application in lignin depolymerization and discovered more active as well as diverse enzymes than previously known. Moreover, the identification of further β-etherases by sequence database mining in the future will be facilitated considerably through our deduced etherase-specific sequence motifs.

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confidence: 62%

Section: Resultsmentioning

confidence: 92%

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confidence: 99%

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Database Mining for Novel Bacterial β-Etherases, Glutathione-Dependent Lignin-Degrading Enzymes

Voß

Heck

Schallmey

et al. 2020

Appl Environ Microbiol

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“…Second, β-etherases (the glutathione S -transferases (GSTs) LigF, LigE, and LigP in SYK-6) replace the β-aryl ether bond of MPHPV with a β-thioether bond involving glutathione (GSH), producing guaiacol and the GSH conjugate, β-glutathionyl-γ-hydroxypropiovanillone (GS-HPV) (20, 21). Known bacterial β-etherases fall into two distinct GST subclasses and are strictly stereospecific for the chirality of the bond's β-carbon (22), with LigE homologues (which include LigP and which are similar to fungal FuA GSTs (23–25)) cleaving the β( R ) isomer of the bond and LigF homologues (which are distinct in amino acid sequence and three-dimensional structure from known members of any previously established GST class (25)) cleaving the β( S ) isomer. Finally, GSH lyases (the GSTs LigG (20) and SYK6GST Nu (26) in SYK-6) remove the GSH moiety from GS-HPV and combine it with another GSH, producing hydroxypropiovanillone (HPV) and GSH disulfide (GSSG).…”

Section: Introductionmentioning

confidence: 99%

“…Finally, GSH lyases (the GSTs LigG (20) and SYK6GST Nu (26) in SYK-6) remove the GSH moiety from GS-HPV and combine it with another GSH, producing hydroxypropiovanillone (HPV) and GSH disulfide (GSSG). LigG homologues, which share some features with Omega-class GSTs (27), are reported to preferentially cleave β( R )-GS-HPV, whereas the Nu-class GST Nu homologues cleave both the β( R ) and β( S ) stereoisomers of GS-HPV with similar catalytic efficiencies (22, 26).…”

Section: Introductionmentioning

confidence: 99%

A heterodimeric glutathione S-transferase that stereospecifically breaks lignin's β(R)-aryl ether bond reveals the diversity of bacterial β-etherases

Kontur

Olmsted

Yusko

et al. 2019

Journal of Biological Chemistry

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Lignin is a heterogeneous polymer of aromatic subunits that is a major component of lignocellulosic plant biomass. Understanding how microorganisms deconstruct lignin is important for understanding the global carbon cycle and could aid in developing systems for processing plant biomass into valuable commodities. Sphingomonad bacteria use stereospecific glutathione S-transferases (GSTs) called β-etherases to cleave the β-aryl ether (β-O-4) bond, the most common bond between aromatic subunits in lignin. Previously characterized bacterial β-etherases are homodimers that fall into two distinct GST subclasses: LigE homologues, which cleave the β(R) stereoisomer of the bond, and LigF homologues, which cleave the β(S) stereoisomer. Here, we report on a heterodimeric β-etherase (BaeAB) from the sphingomonad Novosphingobium aromaticivorans that stereospecifically cleaves the β(R)-aryl ether bond of the di-aromatic compound β-(2-methoxyphenoxy)-γ-hydroxypropiovanillone (MPHPV). BaeAB's subunits are phylogenetically distinct from each other and from other β-etherases, although they are evolutionarily related to LigF, despite the fact that BaeAB and LigF cleave different β-aryl ether bond stereoisomers. We identify amino acid residues in BaeAB's BaeA subunit important for substrate binding and catalysis, including an asparagine that is proposed to activate the GSH cofactor. We also show that BaeAB homologues from other sphingomonads can cleave β(R)-MPHPV and that they may be as common in bacteria as LigE homologues. Our results suggest that the ability to cleave the β-aryl ether bond arose independently at least twice in GSTs and that BaeAB homologues may be important for cleaving the β(R)-aryl ether bonds of lignin-derived oligomers in nature.

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Hemoglobin–Laccase Modifications of Ligninsulfonate: A Promising Synergistic Stratagem for Lignin Biodegradation

Chen

Shi

et al. 2022

Advanced Sustainable Systems

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Multicomponent systems, such as laccase cooperating with other proteins in ligninase, are able to modify the chemical structure of lignin efficiently and opens the door to potential applications. Here, an in‐depth investigation of hemoglobin‐assisted laccase oxidation of soluble lignosulfonate is carried out, using a combination of UV–visible spectroscopy, isothermal titration calorimetry, gel permeation chromatography, Raman spectroscopy, 2D nuclear magnetic resonance spectroscopy, and high‐performance liquid chromatography–mass spectrometry. Intriguingly, hemoglobin enhances the exothermically oxidative process of the laccase reaction. Product characterizations suggest that hemoglobin may preferentially reduce the ratio of guaiacyl/syringyl subunits and promote phenylcoumaran formation simultaneously. The complicated interactions among hemoglobin, laccase, and lignin make a multiple‐component reaction, suggesting that Fe‐containing macromolecules have the capacity to mediate laccase based chemical modifications of lignin.

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Microbial β-etherases and glutathione lyases for lignin valorisation in biorefineries: current state and future perspectives

Cited by 15 publications

References 54 publications

Database Mining for Novel Bacterial β-Etherases, Glutathione-Dependent Lignin-Degrading Enzymes

Database Mining for Novel Bacterial β-Etherases, Glutathione-Dependent Lignin-Degrading Enzymes

A heterodimeric glutathione S-transferase that stereospecifically breaks lignin's β(R)-aryl ether bond reveals the diversity of bacterial β-etherases

Hemoglobin–Laccase Modifications of Ligninsulfonate: A Promising Synergistic Stratagem for Lignin Biodegradation

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