Feruloyl esterases play a key role in the degradation of the intricate structure of the plant cell wall by hydrolysing the ferulate ester groups involved in the cross-linking between hemicelluloses and between hemicellulose and lignin. It belongs to a supramolecular assembly termed a cellulosome. This multienzyme complex possesses in addition to its well-described cellulolytic activity an apparatus specific for xylan degradation. Feruloyl esterases, Cinnamic acid esterases hydrolyze the ferulate groups involved in the crosslinking of arabinoxylans to lignin and thus play a key role in the degradation of the plant cell wall. clotm-xyny corresponds to the feruloyl esterase module from a 5 domain xylanase Xyn10B. This family contains enzymes corresponding to a subset of the Carbohydrate Esterase family CE1 in CAZy - Carbohydrate-Active enZYmes database (CE_1) with Ser His Asp catalytic triad. Here most of the A85-Feruloyl-Esterase are bacterial enzymes but there are few fungi proteins that belong to this family and are farther related to the other fungi feruloyl esterase belonging to other families (Tannase (Aspergillus Niger FaeB) ; 6_AlphaBeta_hydrolase, Lipase_3 (Aspergillus Niger FaeA); Esterase_phb (Penicillium funiculosum FaeB Piromyces equi ESTA). Feruloyl esterases are distributed in different sub-classes type-A B C,D and E and fall respectively in the following families. Type-A in Lipase_3, Type-B in Esterase_phb (PHB depolymerase), Type-C in Tannase, Type-D in FaeC, Type-E in A85-Feruloyl-Esterase, Type-F in BD-FAE
AIMS: A novel ferulic acid esterase gene from rumen fungus Anaeromyces mucronatus was cloned, heteroexpressed in Escherichia coli and characterized. METHODS AND RESULTS: A total of 30 clones exhibiting activity on alpha-naphthyl acetate (alpha-NA) were isolated from an A. mucronatus YE505 cDNA library. Sequence analysis revealed that these clones represented two esterase-coding sequences. The gene, fae1A, showed highest amino acid sequence identity to CE family 1 esterases from anaerobic micro-organisms such as Orpinomyces sp., Ruminococcus albus and Clostridium thermocellum. The gene comprised 828 nucleotides encoding a polypeptide of 275 amino acids. The coding sequence was cloned into the pET30a expression vector and overexpressed in E. coli BL21 (DE3). Gene product Fae1A was found to exhibit activity against a number of substrates including naphthyl fatty acid esters, p-nitrophenyl fatty acid esters and hydroxylcinnamic acid esters. CONCLUSIONS: Fae1A exhibited a lower K(m) and higher catalytic efficiency (k(cat) /K(m) ) on ferulic acid esters than on alpha-NA or p-nitrophenyl acetate, suggesting that it has a higher affinity for ethyl and methyl ferulate than for the acetyl esters. It releases ferulic acid and p-coumaric acid from barley straw. Activity of Fae1A was inhibited by the serine-specific protease inhibitor, phenylmethylsulfonyl fluoride, indicating that a serine residue plays a role in its activity. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first report of characterization of carbohydrate esterase gene from the genus of Anaeromyces.
        
Title: Molecular determinants of substrate specificity in the feruloyl esterase module of xylanase 10B from Clostridium thermocellum Tarbouriech N, Prates JA, Fontes CM, Davies GJ Ref: Acta Crystallographica D Biol Crystallogr, 61:194, 2005 : PubMed
Feruloyl esterases play a key role in the degradation of the intricate structure of the plant cell wall by hydrolysing the ferulate ester groups involved in the cross-linking between hemicelluloses and between hemicellulose and lignin. The structure of the feruloyl esterase module of Clostridium thermocellum cellulosomal xylanase 10B has been reported previously. It displays the alpha/beta hydrolase fold with a classical Ser-His-Asp catalytic triad. Here, the structures of a Ser-Ala mutant of this feruloyl esterase in complexes with methyl syringate, methyl sinapinate and methyl vanillate are described. Substrate binding is accompanied by subtle conformational changes at amino acids Trp982, Met955, Asn1023 and Ile1019 in the ligand-binding cavity. The structural determinants, particularly the m-methoxy substituent, governing the substrate specificity of Xyn10B feruloyl esterase are rationalized.
BACKGROUND:
Degradation of the plant cell wall requires the synergistic action of a consortium of predominantly modular enzymes. In Clostridiae, these biocatalysts are organized into a supramolecular assembly termed a "cellulosome." This multienzyme complex possesses, in addition to its well-described cellulolytic activity, an apparatus specific for xylan degradation. Cinnamic acid esterases hydrolyze the ferulate groups involved in the crosslinking of arabinoxylans to lignin and thus play a key role in the degradation of the plant cell wall in addition to having promising industrial and medical applications.
RESULTS:
We have cloned and overexpressed the feruloyl esterase module from a 5 domain xylanase, Xyn10B from Clostridium thermocellum. The native structure at 1.6 A resolution has been solved with selenomethionine multiple wavelength anomalous dispersion and refined to a final R(free) of 17.8%. The structure of a hydrolytically inactive mutant, S954A, in complex with the reaction product ferulic acid has been refined at a resolution of 1.4 A with an R(free) of 16.0%.
CONCLUSIONS:
The C. thermocellum Xyn10B ferulic acid esterase displays the alpha/beta-hydrolase fold and possesses a classical Ser-His-Asp catalytic triad. Ferulate esterases are characterized by their specificity, and the active center reveals the binding site for ferulic acid and related compounds. Ferulate binds in a small surface depression that possesses specificity determinants for both the methoxy and hydroxyl ring substituents of the substrate. There appears to be a lack of specificity for the xylan backbone, which may reflect the intrinsic chemical heterogeneity of the natural substrate.
        
2 lessTitle: Contributions of a unique beta-clamp to substrate recognition illuminates the molecular basis of exolysis in ferulic acid esterases Gruninger RJ, Cote C, McAllister TA, Abbott DW Ref: Biochemical Journal, 473:839, 2016 : PubMed
Lignocellulosic biomass is a promising renewable resource; however, deconstruction of this material is still the rate-limiting step. Major obstacles in the biocatalytic turnover of lignocellulose are ester-linked decorations that prevent access to primary structural polysaccharides. Enzymes targeting these esters represent promising biotools for increasing bioconversion efficiency. Ruminant livestock are unique in their ability to degrade lignocellulose through the action of their gut microbiome. The anaerobic fungi (phylum Neocallimastigomycota) are key members of this ecosystem that express a large repertoire of carbohydrate-active enzymes (CAZymes) with little sequence identity with characterized CAZymes [Lombard, Golaconda, Drula, Coutinho and Henrissat (2014) Nucleic Acids Res. 42: , D490-D495]. We have identified a carbohydrate esterase family 1 (CE1) ferulic acid esterase (FAE) belonging toAnaeromyces mucronatus(AmCE1/Fae1a), and determined its X-ray structure in both the presence [1.55 A (1 A=0.1 nm)] and absence (1.60 A) of ferulic acid. AmCE1 adopts an alpha/beta-hydrolase fold that is structurally conserved with bacterial FAEs, and possesses a unique loop, termed the beta-clamp, that encloses the ligand. Isothermal titration calorimetry reveals that substrate binding is driven by enthalpic contributions, which overcomes a large entropic penalty. A comparative analysis of AmCE1 with related enzymes has uncovered the apparent structural basis for differential FAE activities targeting cross-linking ferulic acid conjugates compared with terminal decorations. Based on comparisons to structurally characterized FAEs, we propose that the beta-clamp may define the structural basis of exolytic activities in FAEs. This provides a structure-based tool for predicting exolysis and endolysis in CE1. These insights hold promise for rationally identifying enzymes tailored for bioconversion of biomass with variations in cell wall composition.
With increasing focus on sustainable energy, bio-refining from lignocellulosic biomass has become a thrust area of research. With most of the works being focused on biofuels, significant efforts are also being directed towards other value added products. Feruloyl esterases (EC. 3.1.1.73) can be used as a tool for bio-refining of lignocellulosic material for the recovery and purification of ferulic acid and related hydroxycinnamic acids ubiquitously found in the plant cell wall. More and more genes coding for feruloyl esterases have been mined out from various sources to allow efficient enzymatic release of ferulic acid and allied hydroxycinnamic acids (HCAs) from plant-based biomass. A sum up on enzymatic extraction of HCAs and its recovery from less explored agro residual by-products is still a missing link and this review brushes up the achieved landmarks so far in this direction and also covers a detailed patent search on this biomass refining enzyme.
AIMS: A novel ferulic acid esterase gene from rumen fungus Anaeromyces mucronatus was cloned, heteroexpressed in Escherichia coli and characterized. METHODS AND RESULTS: A total of 30 clones exhibiting activity on alpha-naphthyl acetate (alpha-NA) were isolated from an A. mucronatus YE505 cDNA library. Sequence analysis revealed that these clones represented two esterase-coding sequences. The gene, fae1A, showed highest amino acid sequence identity to CE family 1 esterases from anaerobic micro-organisms such as Orpinomyces sp., Ruminococcus albus and Clostridium thermocellum. The gene comprised 828 nucleotides encoding a polypeptide of 275 amino acids. The coding sequence was cloned into the pET30a expression vector and overexpressed in E. coli BL21 (DE3). Gene product Fae1A was found to exhibit activity against a number of substrates including naphthyl fatty acid esters, p-nitrophenyl fatty acid esters and hydroxylcinnamic acid esters. CONCLUSIONS: Fae1A exhibited a lower K(m) and higher catalytic efficiency (k(cat) /K(m) ) on ferulic acid esters than on alpha-NA or p-nitrophenyl acetate, suggesting that it has a higher affinity for ethyl and methyl ferulate than for the acetyl esters. It releases ferulic acid and p-coumaric acid from barley straw. Activity of Fae1A was inhibited by the serine-specific protease inhibitor, phenylmethylsulfonyl fluoride, indicating that a serine residue plays a role in its activity. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first report of characterization of carbohydrate esterase gene from the genus of Anaeromyces.
        
Title: Molecular determinants of substrate specificity in the feruloyl esterase module of xylanase 10B from Clostridium thermocellum Tarbouriech N, Prates JA, Fontes CM, Davies GJ Ref: Acta Crystallographica D Biol Crystallogr, 61:194, 2005 : PubMed
Feruloyl esterases play a key role in the degradation of the intricate structure of the plant cell wall by hydrolysing the ferulate ester groups involved in the cross-linking between hemicelluloses and between hemicellulose and lignin. The structure of the feruloyl esterase module of Clostridium thermocellum cellulosomal xylanase 10B has been reported previously. It displays the alpha/beta hydrolase fold with a classical Ser-His-Asp catalytic triad. Here, the structures of a Ser-Ala mutant of this feruloyl esterase in complexes with methyl syringate, methyl sinapinate and methyl vanillate are described. Substrate binding is accompanied by subtle conformational changes at amino acids Trp982, Met955, Asn1023 and Ile1019 in the ligand-binding cavity. The structural determinants, particularly the m-methoxy substituent, governing the substrate specificity of Xyn10B feruloyl esterase are rationalized.
BACKGROUND:
Degradation of the plant cell wall requires the synergistic action of a consortium of predominantly modular enzymes. In Clostridiae, these biocatalysts are organized into a supramolecular assembly termed a "cellulosome." This multienzyme complex possesses, in addition to its well-described cellulolytic activity, an apparatus specific for xylan degradation. Cinnamic acid esterases hydrolyze the ferulate groups involved in the crosslinking of arabinoxylans to lignin and thus play a key role in the degradation of the plant cell wall in addition to having promising industrial and medical applications.
RESULTS:
We have cloned and overexpressed the feruloyl esterase module from a 5 domain xylanase, Xyn10B from Clostridium thermocellum. The native structure at 1.6 A resolution has been solved with selenomethionine multiple wavelength anomalous dispersion and refined to a final R(free) of 17.8%. The structure of a hydrolytically inactive mutant, S954A, in complex with the reaction product ferulic acid has been refined at a resolution of 1.4 A with an R(free) of 16.0%.
CONCLUSIONS:
The C. thermocellum Xyn10B ferulic acid esterase displays the alpha/beta-hydrolase fold and possesses a classical Ser-His-Asp catalytic triad. Ferulate esterases are characterized by their specificity, and the active center reveals the binding site for ferulic acid and related compounds. Ferulate binds in a small surface depression that possesses specificity determinants for both the methoxy and hydroxyl ring substituents of the substrate. There appears to be a lack of specificity for the xylan backbone, which may reflect the intrinsic chemical heterogeneity of the natural substrate.
The carbohydrate binding module family 48 (CBM48) and carboxy-terminal carbohydrate esterase family 1 (CE1) domains of the multidomain esterase DmCE1B from Dysgonomonas mossii. There are two CE domains in this protein and structure. In ESTHER they correspond to two entries 9bact-f8x1n1.1 and 9bact-f8x1n1.2
The carbohydrate binding module family 48 (CBM48) and carboxy-terminal carbohydrate esterase family 1 (CE1) domains of the multidomain esterase DmCE1B from Dysgonomonas mossii. There are two CE domains in this protein and structure. In ESTHER they correspond to two entries 9bact-f8x1n1.1 and 9bact-f8x1n1.2
The carbohydrate binding module family 48 (CBM48) and carboxy-terminal carbohydrate esterase family 1 (CE1) domains of the multidomain esterase DmCE1B from Dysgonomonas mossii in complex with methyl ferulate
The carbohydrate binding module family 48 (CBM48) and carboxy-terminal carbohydrate esterase family 1 (CE1) domains of the multidomain esterase DmCE1B from Dysgonomonas mossii in complex with methyl ferulate