Degradative GH5 β-1,3-1,4-glucanase PpBglu5A for glucan in Paenibacillus polymyxa KF-1

Non-Catalytic Domains of Glycoside Hydrolase Family 5 from Paenibacillus curdlanolyticus are Important for Promoting Multifunctional Enzyme Activities and Degradation of Agricultural Residues

PcGH5 from Paenibacillus curdlanolyticus strain B-6 is a modular protein consisting of a catalytic domain of glycoside hydrolase family 5 (GH5), and three non-catalytic domains (a family 11 carbohydrate-binding module (CBM11), a fibronectin type 3 (Fn3), and a family 3 carbohydrate-binding module (CBM3). In this study, the recombinants full-length PcGH5 and the catalytic domain (PcGH5_CD) were expressed in Escherichia coli and purified. Most GH5 members exhibit endo-cellulase activity. However, the catalytic domain enzyme of strain B-6 exhibited unique properties, showing multifunctional enzyme activities of endo-cellulase, endo-xylanase, endo-mannanase, and endo-1,3-1,4-β-glucanase. The sequence alignment of PcGH5_CD compared to other characterized GH5 enzymes suggests that the two catalytic residues and the six substrate-binding subsites of endo-cellulases were conserved with other different GH5 enzyme properties. Whereas a few conserved amino acid residues and/or short peptides located outside the active site of the GH5 endo-cellulases may be involved in broad substrate specificity of PcGH5_CD enzyme on xylan, mannan and 1,3-1,4-β-glucan. Moreover, the non-catalytic domains (CBM11-Fn3-CBM3) linked to the GH5 catalytic domain are important for promoting the multifunctional enzyme activities of PcGH5 on the β-1,4 glycosidic linkages of crystalline cellulose, highly branched polysaccharides, and β-1,4-1,6 and β-1,3-1,4 glycosidic linkages of polysaccharides, especially for the polysaccharides complex contained in agricultural residues. The full-length PcGH5 is effective in producing oligosaccharides from agricultural residues without pretreatment. Therefore, it is interesting to use it as a source of prebiotics producer for use in various food products.

Module architecture analysis and application of glycoside hydrolase family 148 thermostable β-1,3-1,4-glucanase

β-1,3-1,4-Glucanases have attracted significant interest because of their potential applications in various food industries. Glycoside hydrolase (GH) family 148 β-1,3-1,4-glucanases exhibit excellent thermal stability and a unique catalytic mechanism, making them particularly promising for certain food processing applications. This study investigated the module architecture enzymatic properties, catalytic mechanisms, and potential applications of a multi-domain β-1,3-1,4-glucanase (EngU) from GH family 148. The overall structure of EngU comprises three independently folding domains, namely the GH148 catalytic domain, CBM4, and the C-terminal domain. The insertion of CBM4 causes the catalytic domain of EngU to be non-contiguous in sequence. The optimum reaction conditions for EngU have been found to be pH 6.0 and 90 °C, demonstrating relatively high thermostability. EngU is an atypical β-1,3-1,4-glucanase, predominantly cleaves the β-1,3 glycosidic bonds in β-1,3-1,4-glucan. Malt saccharification experiments revealed that adding EngU (80 U/g malt) can decreased the viscosity of mash by 6.85 % and the filtration time by 28.83 %. Furthermore, EngU was found to effectively hydrolyze oat bran, producing β-glucooligosaccharides, with the main hydrolysis products being trisaccharide and disaccharide. These results demonstrate the unique module architecture and the application potential of GH family 148 β-1,3-1,4-glucanases, providing valuable insights and resources regarding this category of glycoside hydrolases.

Structural and functional snapshots of a broad-specificity endoglucanase from Thermogutta terrifontis for biomass saccharification

Multifunctionality, processivity, and thermostability are critical for the cost-effective enzymatic saccharification of non-food plant biomass polymers such as β-glucans, celluloses, and xylans to generate biofuels and other valuable products. We present molecular insights into a processive multifunctional endo-1,3-1,4-β-d-glucanase (Tt_End5A) from the hyperthermophilic bacterium Thermogutta terrifontis. Tt_End5A demonstrated activities against a broad spectrum of β-polysaccharides, including barley glucan, lichenan, carboxymethyl cellulose, regenerated amorphous cellulose (RAC), Avicel, xylan, laminarin, mannan, curdlan, xanthan, and various chromogenic substrates at pH 7 and temperatures ranging from 70 to 80°C. The enzyme exhibited a high level of processivity on RAC and retained over 90% activity at 80°C for an extended period, indicating exceptional thermal stability. The 1.20 Å crystal structure of the Tt_End5A catalytic domain revealed an archetypal glycoside hydrolase family 5 (GH5) catalytic TIM-(β/α)8-barrel, supplemented with additional β-strands, elongated α-helices, and a rare cis-non-Pro (His481-cis-Ala482) peptide. A large central cleft was observed in the 3D structure, which is likely related to the enzyme's multifunctionality and processivity. The catalytic domain is preceded by a novel N-terminal multivalent carbohydrate-binding module (CBM) that enhances the enzymatic degradation of insoluble polysaccharides. Mutagenesis studies, ligand interaction analyses, and the structurally conserved positions of E329 and E448 in Tt_End5A suggest that these residues function as the proton donor and nucleophile in the catalytic mechanism. Owing to its multifunctionality and processivity, Tt_End5A can reduce the need for multiple saccharification enzymes to generate fermentable sugars from plant biomass for bioethanol production. Additionally, it holds promise for applications in the pharmaceutical, feed, and food industries.

Crystal structures of Aspergillus oryzae exo-β-(1,3)-glucanase reveal insights into oligosaccharide binding, recognition, and hydrolysis

Exo-β-(1,3)-glucanases are promising enzymes for use in the biofuel industry as they hydrolyse sugars such as laminarin, a major constituent of the algal cell wall. This study reports structural and biochemical characterizations of Aspergillus oryzae exo-β-(1,3)-glucanase (AoBgl) belonging to the GH5 family. Purified AoBgl hydrolyses β-(1,3)-glycosidic linkages of the oligosaccharide laminaritriose and the polysaccharide laminarin effectively. We have determined three high-resolution structures of AoBgl: (a) the apo form at 1.75 Å, (b) the complexed form with bound cellobiose at 1.73 Å and (c) the glucose-bound form at 1.20 Å. The crystal structures, molecular dynamics simulation studies and site-directed mutagenesis reveal the mode of substrate binding and interactions at the active site. The results also indicate that AoBgl effectively hydrolyses trisaccharides and higher oligosaccharides. The findings from our structural and biochemical studies would aid in rational engineering efforts to generate superior AoBgl variants and similar GH5 enzymes for their industrial use.

Elucidation of Domain Function of a Novel Multifunctional Glycoside Hydrolase and Its Use in Efficient Preparation of Oligosaccharides from Kelp Powder

Kelp contained laminarin, cellulose, and alginate as major polysaccharides and could be utilized as functional oligosaccharides. A new multifunctional glycoside hydrolase CelA was identified and characterized for the efficient degradation of kelp powder. It displayed cellulase (2308.38 U/mg), alginate lyase (578.68 U/mg), and laminarinase (720.97 U/mg) activities. It exhibited maximal activity on both sodium alginate and laminarin at 50 °C and pH 8.0, while it could degrade sodium carboxymethylcellulose (CMC-Na) by maximal activity at 40 °C and pH 7.0. The action mode analysis by thin layer chromatography and electrospray ionization mass spectrometry indicated that CelA adopted an endolytic manner to degrade CMC-Na, sodium alginate, and laminarin releasing oligosaccharides with degrees of polymerization (Dps) of 2-5. According to domain analysis, CelA contained a GH5 module and a PL6 module, and both of them exhibited glycoside hydrolase and polysaccharide lyase activity. The docking results revealed that Glu163 and Glu250 are essential in cellulose and laminarin degradation. As to the degradation of alginate, Asn376, Lys436, Arg464, Asp496, and Asn551 could bind alginate and Tyr492 and Lys529 acted as catalytic sites. CelA displayed high hydrolysis efficiency for cellulose, β-glucan, laminarin, alginate, and kelp powder. Thus, it has strong potential in food and feed industries as a catalyst for bioconversion of algal biomass into value-added products oligosaccharides.

Advances in molecular enzymology of β-1,3-glucanases: A comprehensive review

β-1,3-Glucanases are essential enzymes involved in the hydrolysis of β-1,3-glucans, with significant biological and industrial relevance. These enzymes are derived from diverse sources, including bacteria, fungi, plants, and animals, each exhibiting unique substrate specificities and biochemical properties. This review provides an in-depth analysis of the natural sources and ecological roles of β-1,3-glucanases, exploring their enzymatic properties such as optimal pH, temperature, molecular weight, isoelectric points, and kinetic parameters, which are crucial for understanding their functionality and stability. Advances in molecular enzymology are discussed, focusing on gene cloning, expression in systems like Escherichia coli and Pichia pastoris, and structural-functional relationships. The reaction mechanisms and the role of non-catalytic carbohydrate-binding modules in enhancing substrate hydrolysis are examined. Industrial applications of β-1,3-glucanases are highlighted, including the production of β-1,3-glucooligosaccharides, uses in the food industry, biological control of plant pathogens, and nutritional roles. This review aims to provide a foundation for future research, improving the efficiency and robustness of β-1,3-glucanases for various industrial applications.

Purification, characterization, immobilization and applications of an enzybiotic β-1,3-1,4-glucanase produced from halotolerant marine Halomonas meridiana ES021

Extracellular β-1,3-1,4-glucanase-producing strain Halomonas meridiana ES021 was isolated from Gabal El-Zeit off shore, Red Sea, Egypt. The Extracellular enzyme was partially purified by precipitation with 75% acetone followed by anion exchange chromatography on DEAE-cellulose, where a single protein band was determined with molecular mass of approximately 72 kDa. The Km value was 0.62 mg β-1,3-1,4-glucan/mL and Vmax value was 7936 U/mg protein. The maximum activity for the purified enzyme was observed at 40 °C, pH 5.0, and after 10 min of the reaction. β-1,3-1,4-glucanase showed strong antibacterial effect against Bacillus subtilis, Streptococcus agalactiae and Vibrio damsela. It also showed antifungal effect against Penicillium sp. followed by Aspergillus niger. No toxicity was observed when tested on Artemia salina. Semi-purified β-1,3-1,4-glucanase was noticed to be effective in clarification of different juices at different pH values and different time intervals. The maximum clarification yields were 51.61% and 66.67% on mango juice at 40 °C and pH 5.3 for 2 and 4 h, respectively. To our knowledge, this is the first report of β-1,3-1,4-glucanase enzyme from halotolerant Halomonas species.

Structural and biochemical insights into the substrate-binding mechanism of a glycoside hydrolase family 12 β-1,3-1,4-glucanase from Chaetomium sp

β-1,3-1,4-Glucanases are a type of hydrolytic enzymes capable of catalyzing the strict cleavage of β-1,4 glycosidic bonds adjacent to β-1,3 linkages in β-D-glucans and have exhibited great potential in food and feed industrials. In this study, a novel glycoside hydrolase (GH) family 12 β-1,3-1,4-glucanase (CtGlu12A) from the thermophilic fungus Chaetomium sp. CQ31 was identified and biochemically characterized. CtGlu12A was most active at pH 7.5 and 65 °C, respectively, and exhibited a high specific activity of 999.9 U mg^-1 towards lichenin. It maintained more than 80% of its initial activity in a wide pH range of 5.0-11.0, and up to 60 °C after incubation at 55 °C for 60 min. Moreover, the crystal structures of CtGlu12A with gentiobiose and tetrasccharide were resolved. CtGlu12A had a β-jellyroll fold, and performed retaining mechanism with two glutamic acids severing as the catalytic residues. In the complex structure, cellobiose molecule showed two binding modes, occupying subsites -2 to -1 and subsites + 1 to + 2, respectively. The concave cleft made mixed β-1,3-1,4-glucan substrates maintain a bent conformation to fit into the active site. Overall, this study is not only helpful for the understanding of the substrate-binding model and catalytic mechanism of GH 12 β-1,3-1,4-glucanases, but also provides a basis for further enzymatic engineering of β-1,3-1,4-glucanases.