Microbial Glucuronoyl Esterases: 10 Years after Discovery

Biely, Peter

doi:10.1128/aem.02396-16

Cited by 20 publications

(12 citation statements)

References 39 publications

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“…CE15-B comprises mostly fungal enzymes, including CuGE, CiP2, and StGE2, but also enzymes of bacterial origin. Variations in the identity and position of the catalytic acid among members of CE15 have been discussed previously 6,7,[13][14][15]18,27,28 . However, with our direct reference to the α/β-hydrolase superfamily we have been able to obtain a clear division of CE15 enzymes into two subgroups with fundamentally different properties encoded in their structural arrangements.…”

Section: Resultsmentioning

confidence: 99%

The structural basis of fungal glucuronoyl esterase activity on natural substrates

et al. 2020

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Structural and functional studies were conducted of the glucuronoyl esterase (GE) from Cerrena unicolor (CuGE), an enzyme catalyzing cleavage of lignin-carbohydrate ester bonds. CuGE is an α/β-hydrolase belonging to carbohydrate esterase family 15 (CE15). The enzyme is modular, comprised of a catalytic and a carbohydrate-binding domain. SAXS data show CuGE as an elongated rigid molecule where the two domains are connected by a rigid linker. Detailed structural information of the catalytic domain in its apo-and inactivated form and complexes with aldouronic acids reveal well-defined binding of the 4-O-methyl-aD -glucuronoyl moiety, not influenced by the nature of the attached xylo-oligosaccharide. Structural and sequence comparisons within CE15 enzymes reveal two distinct structural subgroups. CuGE belongs to the group of fungal CE15-B enzymes with an open and flat substrate-binding site. The interactions between CuGE and its natural substrates are explained and rationalized by the structural results, microscale thermophoresis and isothermal calorimetry.

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Section: Resultsmentioning

confidence: 99%

The structural basis of fungal glucuronoyl esterase activity on natural substrates

et al. 2020

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“…Notably, enzymes belonging to families GH2 and GH3 were also abundant in the moose rumen microbiome, and predicted to participate in plant cell wall deconstruction ( Svartström et al, 2017 ). Characterized CE15 members display 4- O -methyl-glucuronoyl methylesterase activity, which are thought to hydrolyze ester linkages that may form between hydroxyl groups in lignin and 4- O -methyl- D -glucuronic acid residues in glucuronoxylans that dominate in hardwood fiber ( Biely et al, 2015 ; Biely, 2016 ). Recently, a marine bacterial CE15 enzyme predicted to act on alginates was also reported, suggesting a broader substrate range for this CE family ( De Santi et al, 2016 ; Agger et al, 2017 ).…”

Section: Resultsmentioning

confidence: 99%

Comparative Metagenomics of Cellulose- and Poplar Hydrolysate-Degrading Microcosms from Gut Microflora of the Canadian Beaver (Castor canadensis) and North American Moose (Alces americanus) after Long-Term Enrichment

Wong¹,

Wang²,

Couturier³

et al. 2017

Front. Microbiol.

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To identify carbohydrate-active enzymes (CAZymes) that might be particularly relevant for wood fiber processing, we performed a comparative metagenomic analysis of digestive systems from Canadian beaver (Castor canadensis) and North American moose (Alces americanus) following 3 years of enrichment on either microcrystalline cellulose or poplar hydrolysate. In total, 9,386 genes encoding CAZymes and carbohydrate-binding modules (CBMs) were identified, with up to half predicted to originate from Firmicutes, Bacteroidetes, Chloroflexi, and Proteobacteria phyla, and up to 17% from unknown phyla. Both PCA and hierarchical cluster analysis distinguished the annotated glycoside hydrolase (GH) distributions identified herein, from those previously reported for grass-feeding mammals and herbivorous foragers. The CAZyme profile of moose rumen enrichments also differed from a recently reported moose rumen metagenome, most notably by the absence of GH13-appended dockerins. Consistent with substrate-driven convergence, CAZyme profiles from both poplar hydrolysate-fed cultures differed from cellulose-fed cultures, most notably by increased numbers of unique sequences belonging to families GH3, GH5, GH43, GH53, and CE1. Moreover, pairwise comparisons of moose rumen enrichments further revealed higher counts of GH127 and CE15 families in cultures fed with poplar hydrolysate. To expand our scope to lesser known carbohydrate-active proteins, we identified and compared multi-domain proteins comprising both a CBM and domain of unknown function (DUF) as well as proteins with unknown function within the 416 predicted polysaccharide utilization loci (PULs). Interestingly, DUF362, identified in iron–sulfur proteins, was consistently appended to CBM9; on the other hand, proteins with unknown function from PULs shared little identity unless from identical PULs. Overall, this study sheds new light on the lignocellulose degrading capabilities of microbes originating from digestive systems of mammals known for fiber-rich diets, and highlights the value of enrichment to select new CAZymes from metagenome sequences for future biochemical characterization.

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“…Many pretreatment strategies are focusing on disrupting cellulose crystallinity by employing exposure to high temperatures and alkaline or acidic conditions. Such strategies will cause hydrolysis of most ester-linked LCCs and thereby eliminate the need for glucuronoyl esterases [ 24 ]. However, such approaches also cause lignin to condense and thereby decrease the final value and applicability of the lignin product and inhibits the cellulolytic conversion [ 25 ].…”

Section: Discussionmentioning

confidence: 99%

The natural catalytic function of CuGE glucuronoyl esterase in hydrolysis of genuine lignin–carbohydrate complexes from birch

Mosbech

Holck

Meyer

et al. 2018

Biotechnol Biofuels

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BackgroundGlucuronoyl esterases belong to carbohydrate esterase family 15 and catalyze de-esterification. Their natural function is presumed to be cleavage of ester linkages in lignin–carbohydrate complexes particularly those linking lignin and glucuronoyl residues in xylans in hardwood.ResultsHere, we show for the first time a detailed product profile of aldouronic acids released from birchwood lignin by a glucuronoyl esterase from the white-rot fungus Cerrena unicolor (CuGE). CuGE releases substrate for GH10 endo-xylanase which results in significantly increased product release compared to the action of endo-xylanase alone. CuGE also releases neutral xylo-oligosaccharides that can be ascribed to the enzymes feruloyl esterase side activity as demonstrated by release of ferulic acid from insoluble wheat arabinoxylan.ConclusionThe data verify the enzyme’s unique ability to catalyze removal of all glucuronoxylan associated with lignin and we propose that this is a direct result of enzymatic cleavage of the ester bonds connecting glucuronoxylan to lignin via 4-O-methyl glucuronoyl-ester linkages. This function appears important for the fungal organism’s ability to effectively utilize all available carbohydrates in lignocellulosic substrates. In bioprocess perspectives, this enzyme is a clear candidate for polishing lignin for residual carbohydrates to achieve pure, native lignin fractions after minimal pretreatment.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1075-2) contains supplementary material, which is available to authorized users.

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Microbial Glucuronoyl Esterases: 10 Years after Discovery

Cited by 20 publications

References 39 publications

The structural basis of fungal glucuronoyl esterase activity on natural substrates

The structural basis of fungal glucuronoyl esterase activity on natural substrates

Comparative Metagenomics of Cellulose- and Poplar Hydrolysate-Degrading Microcosms from Gut Microflora of the Canadian Beaver (Castor canadensis) and North American Moose (Alces americanus) after Long-Term Enrichment

The natural catalytic function of CuGE glucuronoyl esterase in hydrolysis of genuine lignin–carbohydrate complexes from birch

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