Cascade enzymatic cleavage of the β-O-4 linkage in a lignin model compound

Rosini, Elena; Allegretti, Chiara; Melis, Roberta; Cerioli, Lorenzo; Conti, Gianluca; Pollegioni, Loredano; D’Arrigo, Paola

doi:10.1039/c5cy01591j

Cited by 38 publications

(32 citation statements)

References 22 publications

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“…2A , D , and E ). Thus, although it has been suggested that LigG can hydrolyze both β-epimers of GS-HPV ( 24 ), this result, along with those published previously ( 21 ), supports the hypothesis that LigG has a strong preference for β( R )-GS-HPV. This direct comparison of substrate conversion to products in assays that differ only in the addition of LigG or NaGST NU allows us to conclude that use of the latter enzyme has advantages owing to its greater ability to release HPV from both GS-HPV epimers under comparable conditions in vitro .…”

Section: Discussionsupporting

confidence: 89%

“…From information available in the literature, it has remained unclear whether the GSH lyase from Sphingobium strain SYK-6, LigG, has a preference for β( R )-GS-HPV ( 18 , 21 ) or is capable of cleaving the thioether linkages in both β( R )-GS-HPV and β( S )-GS-HPV ( 24 ). As the presence of NaGST NU resulted in cleavage of both β( R )-GS-HPV and β( S )-GS-HPV in this coupled reaction system ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The diaromatic β-ether-linked guaiacylglycerol-β-guaiacyl ether (GGE [ Fig. 1B ]) lignin model compound has been used as a substrate to identify the following three enzymatic steps in cleavage of β-ether linkages in vitro ( 17 – 21 ): (i) a set of dehydrogenases catalyze NAD (NAD + )-dependent α-oxidation of GGE to GGE-ketone, also referred to as α-(2-methoxyphenoxy)-β-hydroxypropiovanillone (MPHPV), and NADH ( 19 , 22 ); (ii) β-etherases, members of the glutathione S -transferase (GST) superfamily, carry out glutathione (GSH)-dependent cleavage of GGE-ketone, releasing guaiacol and β-S-glutathionyl-γ-hydroxypropiovanillone (GS-HPV) ( 18 , 21 , 23 ); and (iii) one or more glutathione lyases catalyze GSH-dependent cleavage of GS-HPV, yielding glutathione disulfide (GSSG) and γ-hydroxypropiovanillone (HPV) ( 18 , 21 , 24 ; W. S. Kontur, C. Bingman, C. Olmstead, D. Wassarman, A. Ulbrich, D. L. Gall, R. W. Smith, L. M. Yusko, B. G. Fox, D. R. Noguera, J. J. Coon, and T. J. Donohue, submitted for publication).…”

Section: Introductionmentioning

confidence: 99%

“…The final step is the GSH-dependent cleavage of the GS-HPV epimers, yielding GSSG and HPV as coproducts. LigG has been shown to cleave both β( R )-GS-HPV and β( S )-GS-HPV ( 24 ), although it appears to have a strong preference for the former ( 18 , 21 ). Recently, a GSH transferase from Novosphingobium aromaticivorans DSM12444 (NaGST NU ; Saro_2595 in GenBank assembly GCA_000013325.1 ) (Kontur et al, submitted) has been shown to have high activity with β( R )-GS-HPV and β( S )-GS-HPV both in vivo and in vitro , producing HPV and GSSG as products ( Fig.…”

Section: Introductionmentioning

confidence: 99%

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In Vitro Enzymatic Depolymerization of Lignin with Release of Syringyl, Guaiacyl, and Tricin Units

Gall

Kontur

Lan

et al. 2018

Appl Environ Microbiol

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New environmentally sound technologies are needed to derive valuable compounds from renewable resources. Lignin, an abundant polymer in terrestrial plants comprised predominantly of guaiacyl and syringyl monoaromatic phenylpropanoid units, is a potential natural source of aromatic compounds. In addition, the plant secondary metabolite tricin is a recently discovered and moderately abundant flavonoid in grasses. The most prevalent interunit linkage between guaiacyl, syringyl, and tricin units is the β-ether linkage. Previous studies have shown that bacterial β-etherase pathway enzymes catalyze glutathione-dependent cleavage of β-ether bonds in dimeric β-ether lignin model compounds. To date, however, it remains unclear whether the known β-etherase enzymes are active on lignin polymers. Here we report on enzymes that catalyze β-ether cleavage from bona fide lignin, under conditions that recycle the cosubstrates NAD+ and glutathione. Guaiacyl, syringyl, and tricin derivatives were identified as reaction products when different model compounds or lignin fractions were used as substrates. These results demonstrate an in vitro enzymatic system that can recycle cosubstrates while releasing aromatic monomers from model compounds as well as natural and engineered lignin oligomers. These findings can improve the ability to produce valuable aromatic compounds from a renewable resource like lignin.IMPORTANCE Many bacteria are predicted to contain enzymes that could convert renewable carbon sources into substitutes for compounds that are derived from petroleum. The β-etherase pathway present in sphingomonad bacteria could cleave the abundant β–O–4-aryl ether bonds in plant lignin, releasing a biobased source of aromatic compounds for the chemical industry. However, the activity of these enzymes on the complex aromatic oligomers found in plant lignin is unknown. Here we demonstrate biodegradation of lignin polymers using a minimal set of β-etherase pathway enzymes, the ability to recycle needed cofactors (glutathione and NAD+) in vitro, and the release of guaiacyl, syringyl, and tricin as depolymerized products from lignin. These observations provide critical evidence for the use and future optimization of these bacterial β-etherase pathway enzymes for industrial-level biotechnological applications designed to derive high-value monomeric aromatic compounds from lignin.

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Section: Discussionsupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

In Vitro Enzymatic Depolymerization of Lignin with Release of Syringyl, Guaiacyl, and Tricin Units

Gall

Kontur

Lan

et al. 2018

Appl Environ Microbiol

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“…On the other hand, LigG had little to no activity with (␤S)-GS-HPV, suggesting involvement of an alternative GST in the conversion of (␤S)-GS-HPV (15,18). Recently, further detailed biochemical characterization of the ␤-aryl ether catabolic enzymes of SYK-6 and their orthologs in other bacterial strains, and structural analyses of LigD, LigL, LigE, LigF, and LigG have been performed (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29). In addition, Erythrobacter sp.…”

mentioning

confidence: 99%

Bacterial Catabolism of β-Hydroxypropiovanillone and β-Hydroxypropiosyringone Produced in the Reductive Cleavage of Arylglycerol-β-Aryl Ether in Lignin

Higuchi

Aoki

Takenami

et al. 2018

Appl Environ Microbiol

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sp. strain SYK-6 converts four stereoisomers of arylglycerol-β-guaiacyl ether into achiral β-hydroxypropiovanillone (HPV) via three stereospecific reaction steps. Here, we determined the HPV catabolic pathway and characterized the HPV catabolic genes involved in the first two steps of the pathway. In SYK-6 cells, HPV was oxidized to vanilloyl acetic acid (VAA) via vanilloyl acetaldehyde (VAL). The resulting VAA was further converted into vanillate through the activation of VAA by coenzyme A. A syringyl-type HPV analog, β-hydroxypropiosyringone (HPS), was also catabolized via the same pathway. SLG_12830 (), which belongs to the glucose-methanol-choline oxidoreductase family, was isolated as the HPV-converting enzyme gene. An mutant completely lost the ability to convert HPV and HPS, indicating that is essential for the conversion of both the substrates. HpvZ produced in oxidized both HPV and HPS and other 3-phenyl-1-propanol derivatives. HpvZ localized to both the cytoplasm and membrane of SYK-6 and used ubiquinone derivatives as electron acceptors. Thirteen gene products of the 23 aldehyde dehydrogenase (ALDH) genes in SYK-6 were able to oxidize VAL into VAA. Mutant analyses suggested that multiple ALDH genes, including SLG_20400, contribute to the conversion of VAL. We examined whether the genes encoding feruloyl-CoA synthetase () and feruloyl-CoA hydratase/lyase ( and ) are involved in the conversion of VAA. Only FerA exhibited activity toward VAA; however, disruption of did not affect VAA conversion. These results indicate that another enzyme system is involved in VAA conversion. Cleavage of the β-aryl ether linkage is the most essential process in lignin biodegradation. Although the bacterial β-aryl ether cleavage pathway and catabolic genes have been well documented, there have been no reports regarding the catabolism of HPV or HPS, the products of cleavage of β-aryl ether compounds. HPV and HPS have also been found to be obtained from lignin by chemoselective catalytic oxidation by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone/-butyl nitrite/O, followed by cleavage of the β-aryl ether with zinc. Therefore, value-added chemicals are expected to be produced from these compounds. In this study, we determined the SYK-6 catabolic pathways for HPV and HPS and identified the catabolic genes involved in the first two steps of the pathways. Since SYK-6 catabolizes HPV through 2-pyrone-4,6-dicarboxylate, which is a building block for functional polymers, characterization of HPV catabolism is important not only for understanding the bacterial lignin catabolic system but also for lignin utilization.

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Lignin valorization using biological approach

Singhvi

Kim

2020

Biotech and App Biochem

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Due to the structural complexity and recalcitrance nature of lignin, its depolymerization into monomeric units becomes one of the biggest challenges in the bioconversion of lignin into value-added products. Depolymerization of lignin produces a blend of many compounds that are problematic for isolating components in a cost-effective way. Lignin valorization using a biological approach facilitates sustainable and commercially viable biorefineries. The use of microbes for the conversion of depolymerized lignin compounds into target products can be a solution to the heterogeneity issue. Several studies have been carried out to develop robust strains that can utilize all relevant lignin-derived compounds, but constructing these strains is difficult. As an alternative, designing multiple microbes to convert a mixture of various compounds into the desired product seems realistic. This review provides an overview of lignin bioconversion using various approaches such as metabolic engineering and synthetic biology. Ligninolytic strains have a broad enzymatic machine for depolymerization of lignin and its conversion into intermediates such as catechol or protocatechuate. These intermediates can be further converted to metabolite products such as polyhydroxyalkanoates and triacylglycerol. Synthetic biology offers encouraging methodologies to construct pathways for lignin conversion and to engineer ligninolytic microbes as prospective strains for lignin bioconversion. ©

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Cascade enzymatic cleavage of the β-O-4 linkage in a lignin model compound

Cited by 38 publications

References 22 publications

In Vitro Enzymatic Depolymerization of Lignin with Release of Syringyl, Guaiacyl, and Tricin Units

In Vitro Enzymatic Depolymerization of Lignin with Release of Syringyl, Guaiacyl, and Tricin Units

Bacterial Catabolism of β-Hydroxypropiovanillone and β-Hydroxypropiosyringone Produced in the Reductive Cleavage of Arylglycerol-β-Aryl Ether in Lignin

Lignin valorization using biological approach

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