Versatile high resolution oligosaccharide microarrays for plant glycobiology and cell wall research.
Pedersen, H. L., Fangel, J. U., McCleary, B., Ruzanski, C., Rydahl, M. G., Ralet, M. C., Farkas, V., Von Schantz, L., Marcus, S. E., Andersen, M.C. F., Field, R., Ohlin, M., Knox, J. P., Clausen, M. H. & Willats, W. G. T. (2012). Journal of Biological Chemistry, 287(47), 39429-39438.
Microarrays are powerful tools for high throughput analysis, and hundreds or thousands of molecular interactions can be assessed simultaneously using very small amounts of analytes. Nucleotide microarrays are well established in plant research, but carbohydrate microarrays are much less established, and one reason for this is a lack of suitable glycans with which to populate arrays. Polysaccharide microarrays are relatively easy to produce because of the ease of immobilizing large polymers noncovalently onto a variety of microarray surfaces, but they lack analytical resolution because polysaccharides often contain multiple distinct carbohydrate substructures. Microarrays of defined oligosaccharides potentially overcome this problem but are harder to produce because oligosaccharides usually require coupling prior to immobilization. We have assembled a library of well characterized plant oligosaccharides produced either by partial hydrolysis from polysaccharides or by de novo chemical synthesis. Once coupled to protein, these neoglycoconjugates are versatile reagents that can be printed as microarrays onto a variety of slide types and membranes. We show that these microarrays are suitable for the high throughput characterization of the recognition capabilities of monoclonal antibodies, carbohydrate-binding modules, and other oligosaccharide-binding proteins of biological significance and also that they have potential for the characterization of carbohydrate-active enzymes.
Crystal structures of the family 9 carbohydrate-binding module from Thermotoga maritima xylanase 10A in native and ligand-bound forms.
Notenboom, V., Boraston, A. B., Kilburn, D. G. & Rose, D. R. (2001). Biochemistry, 40(21), 6248-6256.
The C-terminal module of the thermostable Thermotoga maritima xylanase 10A (CBM9-2) is a family 9 carbohydrate-binding module that binds to amorphous and crystalline cellulose and a range of soluble di- and monosaccharides as well as to cello and xylo oligomers of different degrees of polymerization [Boraston, A. B., Creagh, A. L., Alam, Md. M., Kormos, J. M., Tomme, P., Haynes, C. A., Warren, R. A. J., and Kilburn, D. G. (2001) Biochemistry 40, 6240−6247]. The crystal structure of CBM9-2 has been determined by the multiwavelength anomalous dispersion method to 1.9 Å resolution. CBM9-2 assumes a β-sandwich fold and contains three metal binding sites. The bound metal atoms, which are most likely calcium cations, are in an octahedral coordination. The crystal structures of CBM9-2 in complex with glucose and cellobiose were also determined in order to identify the sugar-binding site and provide insight into the structural basis for sugar binding by CBM9-2. The sugar-binding site is a solvent-exposed slot sufficient in depth, width, and length to accommodate a disaccharide. Two tryptophan residues are stacked together on the surface of the protein forming the sugar-binding site. From the complex structures with glucose and cellobiose, it was inferred that CBM9-2 binds exclusively to the reducing end of mono-, di-, and oligosaccharides with an intricate hydrogen-bonding network involving mainly charged residues, as well as stacking interactions by Trp175 and Trp71. The binding interactions are limited to disaccharides as was expected from calorimetric data. Comparison of the glucose and cellobiose complexes revealed surprising differences in binding of these two substrates by CBM9-2. Cellobiose was found to bind in a distinct orientation from glucose, while still maintaining optimal stacking and electrostatic interactions with the reducing end sugar.
Mixed‐linkage (1→ 3, 1→ 4)‐β-D‐glucan is a major hemicellulose of Equisetum (horsetail) cell walls.
Fry, S. C., Nesselrode, B. H. W. A., Miller, J. G. & Mewburn, B. R. (2008). New Phytologist, 179(1), 104-115.
Mixed-linkage (1→3,1→4)-β-D-glucan (MLG) is a hemicellulose reputedly confined to certain Poales. Here, the taxonomic distribution of MLG, and xyloglucan, especially in early-diverging pteridophytes, has been re-investigated. Polysaccharides were digested with lichenase and xyloglucan endoglucanase (XEG), which specifically hydrolyse MLG and xyloglucan, respectively. The oligosaccharides produced were analysed by thin-layer chromatography (TLC), high-pressure liquid chromatography (HPLC) and alkaline peeling. Lichenase yielded oligo-β-glucans from all Equisetum species tested (Equisetum arvense, Equisetum fluviatile, Equisetum scirpoides, Equisetum sylvaticum and Equisetum ×trachyodon). The major product was the tetrasaccharide β-glucosyl-(1→4)-β-glucosyl-(1→4)-β-glucosyl-(1→3)-glucose (G4G4G3G), which was converted to cellotriose by alkali, confirming its structure. Minor products included G3G, G4G3G and a nonasaccharide. By contrast, poalean MLGs yielded G4G3G > G4G4G3G > nonasaccharide > dodecasaccharide. No other pteridophytes tested contained MLG, including Psilotum and eusporangiate ferns. No MLG was found in lycopodiophytes, bryophytes, Chara or Nitella. XEG digestion showed that Equisetum xyloglucan has unusual repeat units. Equisetum, an exceedingly isolated genus whose closest living relatives diverged > 380 million years ago, has evolved MLG independently of the Poales. Equisetum and poalean MLGs share basic structural motifs but also exhibit clear-cut differences. Equisetum MLG is firmly wall-bound, and may tether neighbouring microfibrils. It is also suggested that MLG acts as a template for silica deposition, characteristic of grasses and horsetails.
Kinetics of the enzymatic cellulose hydrolysis by the endoglucanase from the extremophile S. solfataricus.
Bonhage, B., Seiferheld, B. & Spiess, A. C. (2013). In Kraslawski A, Turunen I (eds.). Proceedings of the 23rd European Symposium on Computer Aided Process Engineering, 23, 85-90.
The hydrolysis of cellulose is a necessary step to provide sugars from biomass, e.g. for fermentation. A promising approach is to hydrolyse cellulose enzymatically. Naturally, cellulolytic enzymes appear in mixtures of at least four different enzyme activities. Until now, research has focused on these enzyme mixtures. But, to accurately describe cellulose hydrolysis, it is essential to identify the individual kinetic parameters of the employed cellulases. Therefore, we investigated the behaviour of the extremophile endoglucanase (EG) SSO1354 from S. solfataricus on cello-oligomers (COs) to determine its kinetic performance. The properties of interest were the binding affinity as function of the chain length of the cellulose as well as inhibitory and activating effects of short COs. We monitored the evolution of the chain length distribution over the reaction time using thin layer chromatography and the formation of reducing sugars with a colorimetric assay. According to the measurements, the cellulase requires a chain length of four or more glucose units to be catalytically active and the enzyme gets more active with increasing chain length. Also, cellotriose (C3) is an inhibitor for the used EG, and cellobiose (C2) seems to be an enzyme activator, in contrast to literature. With the obtained results it should be possible to mechanistically describe the hydrolysis of cellulose.
New insights into the role of the thumb-like loop in GH-11 xylanases.
Paës, G., Tran, V., Takahashi, M., Boukari, I. & O'Donohue, M. J. (2007). Protein Engineering Design and Selection, 20(1), 15-23.
GH-11 xylanases are highly specific and possess a thumb-shaped loop, a unique structure among enzymes with a jelly-roll scaffold. To investigate this structure, in vitro mutagenesis was performed on a GH-11 xylanase (Tx-Xyl) from Thermobacillus xylanilyticus. Targets were the conserved amino acids Pro114-Ser115-Ile116 that are located at the thumb's tip and Thr121 and Tyr111, linker residues that connect the thumb to the main enzyme scaffold. Site-saturation mutagenesis provided an active variant that possesses a new triplet (Pro114-Gly115-Cys116), not found in naturally occurring GH-11 xylanases. The Kcat value for xylan hydrolysis catalysed by this mutant was increased by 20%. Re-positioning of the thumb through the deletion of the linker residues produced different effects. As predicted by in silico analyses, deletion of Thr121 had drastic consequences on activity, whereas deletion of Tyr111 only affected (4-fold decrease) Kcat. Finally, deletion mutagenesis was used to create a thumbless variant that was almost catalytically inactive. Fluorescence titration with xylotetraose and xylopentaose revealed that this thumb-deleted xylanase retained the ability to bind substrates. This binding was comparable to that of the wild-type enzyme. Additionally, unlike wild-type Tx-Xyl, the thumb-deleted xylanase efficiently bound cellotetraose, although no cellulose hydrolysing activity was detected. Overall, these data show that the thumb is a key determinant for substrate selection and support previous data that suggest that it plays a role in the catalytic process.
Isolation and identification of phenolic glucosides from thermally treated olive oil byproducts.
Rubio-Senent, F., Lama-Muñoz, A., Rodríguez-Gutiérrez, G. & Fernández-Bolaños, J. (2013). Journal of Agricultural and Food Chemistry, 61(6), 1235-1248.
A liquid phase rich in bioactive compounds, such as phenols and sugars, is obtained from olive oil waste by novel thermal treatment. Two groups of fractions with common characteristics were obtained and studied after thermal treatment, acid hydrolysis, and separation by ultrafiltration, chromatography, and finally Superdex Peptide HR. In the first group, which eluted at the same time as oligosaccharides with a low DP (4–2), an oleosidic secoiridoid structure conjugated to a phenolic compound (hydroxytyrosol) was identified as oleuropeinic acid, and three possible structures were detected. In the second group, glucosyl structures formed by hydroxytyrosol and one, two, or three units of glucose or by tyrosol and glucose have been proposed. Verbascoside, a heterosidic ester of caffeic acid, in which hydroxytyrosol is linked to rhamnose–glucose or one of its isomers was also identified. Neutral oligosaccharides bound to a phenol-containing compound could be antioxidant-soluble fibers with bioactive properties.
Engineering of Family-5 Glycoside Hydrolase (Cel5A) from an Uncultured Bacterium for Efficient Hydrolysis of Cellulosic Substrates.
Telke, A. A., Zhuang, N., Ghatge, S. S., Lee, S. H., Shah, A. A., Khan, H., Um, Y., Shin, H. D., Chung, Y. R., Lee, K. H. & Kim, S. W. (2013). PloS one, 8(6), e65727.
Cel5A, an endoglucanase, was derived from the metagenomic library of vermicompost. The deduced amino acid sequence of Cel5A shows high sequence homology with family-5 glycoside hydrolases, which contain a single catalytic domain but no distinct cellulose-binding domain. Random mutagenesis and cellulose-binding module (CBM) fusion approaches were successfully applied to obtain properties required for cellulose hydrolysis. After two rounds of error-prone PCR and screening of 3,000 mutants, amino acid substitutions were identified at various positions in thermotolerant mutants. The most heat-tolerant mutant, Cel5A_2R2, showed a 7-fold increase in thermostability. To enhance the affinity and hydrolytic activity of Cel5A on cellulose substrates, the family-6 CBM from Saccharophagus degradans was fused to the C-terminus of the Cel5A_2R2 mutant using overlap PCR. The Cel5A_2R2-CBM6 fusion protein showed 7-fold higher activity than the native Cel5A on Avicel and filter paper. Cellobiose was a major product obtained from the hydrolysis of cellulosic substrates by the fusion enzyme, which was identified by using thin layer chromatography analysis.
Deciphering the synergism of endogenous glycoside hydrolase families 1 and 9 from Coptotermes gestroi.
Franco Cairo, J. P. L., Oliveira, L. C., Uchima, C. A., Alvarez, T. M., Citadini, A. P. D. S., Cota, J., Costa-Leonardo, F., Costa-Leonardo, A. M., Carazzolle, M. F., Costa, F. F., Pereira, G. A. G. & Squina, F. M. (2013). Insect Biochemistry and Molecular Biology, 43(10), 970-981.
Termites can degrade up to 90% of the lignocellulose they ingest using a repertoire of endogenous and symbiotic degrading enzymes. Termites have been shown to secrete two main glycoside hydrolases, which are GH1 (EC 188.8.131.52) and GH9 (EC 184.108.40.206) members. However, the molecular mechanism for lignocellulose degradation by these enzymes remains poorly understood. The present study was conducted to understand the synergistic relationship between GH9 (CgEG1) and GH1 (CgBG1) from Coptotermes gestroi, which is considered the major urban pest of São Paulo State in Brazil. The goal of this work was to decipher the mode of operation of CgEG1 and CgBG1 through a comprehensive biochemical analysis and molecular docking studies. There was outstanding degree of synergy in degrading glucose polymers for the production of glucose as a result of the endo-β-1,4-glucosidase and exo-β-1,4-glucosidase degradation capability of CgEG1 in concert with the high catalytic performance of CgBG1, which rapidly converts the oligomers into glucose. Our data not only provide an increased comprehension regarding the synergistic mechanism of these two enzymes for cellulose saccharification but also give insight about the role of these two enzymes in termite biology, which can provide the foundation for the development of a number of important applied research topics, such as the control of termites as pests as well as the development of technologies for lignocellulose-to-bioproduct applications.
Revisiting the Brønsted acid catalyzed hydrolysis kinetics of polymeric carbohydrates in ionic liquids by in situ ATR-FTIR spectroscopy.
Kunov-Kruse, A. J., Riisager, A., Saravanamurugan, S., Berg, R. W., Kristensen, S. B. & Fehrmann, R. (2013). Green Chemistry, 15(10), 2843-2848.
A new versatile method to measure rates and determine activation energies for the Brønsted acid catalysed hydrolysis of cellulose and cellobiose (and other polymeric carbohydrates) in ionic liquids is demonstrated by following the C–O stretching band of the glycoside bond with in situ ATR-FTIR. An activation energy in excellent agreement with the literature was determined for cellulose hydrolysis, whereas a distinctly lower activation energy was determined for cellobiose hydrolysis. The methodology also allowed to independently determine activation energies for the formation of 5-hydroxymethylfurfural in the systems.
Characterization and crystal structure of a thermostable glycoside hydrolase family 45 1,4-β-endoglucanase from Thielavia terrestris.
Gao, J., Huang, J. W., Li, Q., Liu, W., Ko, T. P., Zheng, Y., Xiao, X., Kuo, C. J., Chen, C. C. & Guo, R. T. (2017). Enzyme and Microbial Technology, 99, 32-37.
1,4-β-Endoglucanase is one of the most important biocatalysts in modern industries. Here, a glycoside hydrolase (GH) family 45 endoglucanase from thermophilic fungus Theilavia terrestris (TtCel45A) was expressed in Pichia pastoris. The recombinant protein shows optimal activity at 60° C, pH 4-5. The enzyme exhibits extraordinary thermostability that more than 80% activity was detected after heating at 80° C for 2.5 hours. The high resolution crystal structures of apo-form enzyme and that in complex with cellobiose and cellotetraose were solved to 1.36-1.58 Å. The protein folds into two overall regions: one is a six-stranded β-barrel, and the other one consists of several extended loops. Between the two regions lies the substrate-binding channel, which is an open cleft spanning across the protein surface. A continuous substrate-binding cleft from subsite −4 to +3 were clearly identified in the complex structures. Notably, the flexible V–VI loop ( 113Gly-114Gly-115Asp-116Leu-117Gly-118Ser) is found to open in the presence of −1 sugar, with D115 and L116 swung away to yield a space to accommodate the catalytic acid D122 and the 2,5B boat conformation of −1 sugar during transition state. Collectively, we characterized the enzyme properties of P. pastoris-expressed TtCel45A and solved high-resolution crystal structures of the enzyme. These results are of great interests in industrial applications and provide new insights into the fundamental understanding of enzyme catalytic mechanism of GH45 endoglucanases.
Unraveling the secretome of Termitomyces clypeatus grown on agroresidues as a potential source for bioethanol production.
Mukherjee, S. & Khowala, S. (2016). Process Biochemistry, 51(11), 1793-1807.
Termitomyces clypeatus MTCC 5091 is an edible mushroom and is prized for its nutritional value as well as for harboring plethora of enzymes essential for carbohydrate degradation. T. clypeatus when grown on agricultural based carbon sources efficiently induced high quantities of lignocellulolytic enzymes in the secretome. Optimization in tamarind kernal powder (TKP) media through response surface methodology enhanced the enzyme yields by several folds. Correlation between extracellular protein productions of the fungus with respect to its specific growth rate established that secreted proteins were produced most efficiently at low specific growth rates. Proteins released in the T. clypeatus secretome were quantified and identified using SDS-PAGE, 2D gel electrophoreses, zymography and matrix-assisted laser desorption mass spectrometry. 36 proteins identified from the protein spots belonged majority to glucosyl hydrolase family, transporters, uncharacterized and hypothetical proteins. The potential synergistic interactions between the cellulases and xylanases in enzyme preparations of T. clypeatus during hydrolysis of steam pretreated bagasse (SPB) showed improved hydrolysis efficiency and enhanced rate of hydrolysis as observed in high performance liquid chromatograpy. The changes in the ultra-structure of SPB after 12 h enzymatic hydrolysis were observed by scanning electron microscopy. The hydrolysates obtained produced ~7.2 g/L ethanol after 6 h fermentation determined by gas chromatography.
A thermostable Gloeophyllum trabeum xylanase with potential for the brewing industry.
Wang, X., Luo, H., Yu, W., Ma, R., You, S., Liu, W., Hou, L., Zheng, F., Xie, X. & Yao, B. (2016). Food Chemistry, 199, 516-523.
A xylanase gene of glycoside hydrolase family 10, GtXyn10, was cloned from Gloeophyllum trabeum CBS 900.73 and expressed in Pichia pastoris GS115. Purified recombinant GtXyn10 exhibited significant activities to xylan (100.0%), lichenan (11.2%), glucan (15.2%) and p-nitrophenol-β-cellobiose (18.6%), demonstrated the maximum xylanase and glucanase activities at pH 4.5-5.0 and 75°C, retained stability over the pH range of 2.0-7.5 and at 70°C, and was resistant to pepsin and trypsin, most metal ions and SDS. Multiple sequence alignment and modeled-structure analysis identified a unique Gly48 in GtXyn10, and site-directed mutagenesis of Gly48 to Lys improved the temperature optimum up to 80°C. Under simulated mashing conditions, GtXyn10 (80 U) reduced the mash viscosity by 12.8% and improved the filtration rate by 31.3%. All these properties above make GtXyn10 attractive for potential applications in the feed and brewing industries.
Heterologous expression of a GH3 β-glucosidase from Neurospora crassa in Pichia pastoris with high purity and its application in the hydrolysis of soybean isoflavone glycosides.
Pei, X., Zhao, J., Cai, P., Sun, W., Ren, J., Wu, Q., Zhang, S. & Tian, C. (2016). Protein expression and Purification, 119, 75-84.
Previous studies have shown isoflavone aglycones to have more biological effects than their counterparts, isoflavone glycones. Some β-glucosidases can hydrolyze isoflavone glucosides to release aglycones, and discovery of these has attracted great interest. A glycoside hydrolase (GH) family 3 β-glucosidase (bgl2) gene from Neurospora crassa was heterologously expressed in Pichia pastoris with high purity. The recombinant BGL2 enzyme displayed its highest activity at pH 5.0 and 60°C, and had its maximum activity against p-nitrophenyl-β-D-glucopyranoside (pNPG) (143.27 ± 4.79 U/mg), followed by cellobiose (74.99 ± 0.78 U/mg), gentiobiose (47.55 ± 0.15 U/mg), p-nitrophenyl-β-D-cellobioside (p NPC) (40.07 ± 0.87 U/mg), cellotriose (12.31 ± 0.36 U/mg) and cellotetraose (9.04 ± 0.14 U/mg). The kinetic parameters of Km and Vmax were 0.21 ± 0.01 mM and 147.93 ± 2.77 µM/mg/min for pNPG. The purified enzyme showed a heightened ability to convert the major soybean isoflavone glycosides (daidzin, genistin and glycitin) into their corresponding aglycone forms (daidzien, genistein and glycitein). With this activity against soybean isoflavone glycosides, BGL2 shows great potential for applications in the food, animal feed, and pharmaceutical industries.
Application of carbohydrate arrays coupled with mass spectrometry to detect activity of plant-polysaccharide degradative enzymes from the fungus Aspergillus niger.
van Munster, J. M., Thomas, B., Riese, M., Davis, A. L., Gray, C. J., Archer, D. B. & Flitsch, S. L. (2017). Scientific Reports, 7.
Renewables-based biotechnology depends on enzymes to degrade plant lignocellulose to simple sugars that are converted to fuels or high-value products. Identification and characterization of such lignocellulose degradative enzymes could be fast-tracked by availability of an enzyme activity measurement method that is fast, label-free, uses minimal resources and allows direct identification of generated products. We developed such a method by applying carbohydrate arrays coupled with MALDI-ToF mass spectrometry to identify reaction products of carbohydrate active enzymes (CAZymes) of the filamentous fungus Aspergillus niger. We describe the production and characterization of plant polysaccharide-derived oligosaccharides and their attachment to hydrophobic self-assembling monolayers on a gold target. We verify effectiveness of this array for detecting exo- and endo-acting glycoside hydrolase activity using commercial enzymes, and demonstrate how this platform is suitable for detection of enzyme activity in relevant biological samples, the culture filtrate of A. niger grown on wheat straw. In conclusion, this versatile method is broadly applicable in screening and characterisation of activity of CAZymes, such as fungal enzymes for plant lignocellulose degradation with relevance to biotechnological applications as biofuel production, the food and animal feed industry.
RP-UHPLC-UV-ESI-MS/MS analysis of LPMO generated C4-oxidized gluco-oligosaccharides after non-reductive labeling with 2-aminobenzamide.
Frommhagen, M., van Erven, G., Sanders, M., van Berkel, W. J., Kabel, M. A. & Gruppen, H. (2017). Carbohydrate Research, In Press.
Lytic polysaccharide monooxygenases (LPMOs) are able to cleave recalcitrant polysaccharides, such as cellulose, by oxidizing the C1 and/or C4 atoms. The analysis of the resulting products requires a variety of analytical techniques. Up to now, these techniques mainly focused on the identification of non-oxidized and C1-oxidized oligosaccharides. The analysis of C4-oxidized gluco-oligosaccharides is mostly performed by using high pressure anion exchange chromatography (HPAEC). However, the alkaline conditions used during HPAEC analysis lead to tautomerization of C4-oxidized gluco-oligosaccharides, which limits the use of this technique. Here, we describe the use of reverse phase-ultra high performance liquid chromatography (RP-UHPLC) in combination with non-reductive 2-aminobenzamide (2-AB) labeling. Non-reductive 2-AB labeling enabled separation of C4-oxidized gluco-oligosaccharides from their non-oxidized counterparts. Moreover, RP-UHPLC does not require buffered mobile phases, which reduce mass spectrometry (MS) sensitivity. The latter is seen as an advantage over other techniques such as hydrophilic interaction liquid chromatography and porous graphitized carbon coupled to MS. RP-UHPLC coupled to UV detection and mass spectrometry allowed the identification of both labeled non-oxidized and C4-oxidized oligosaccharides. Non-reductive labeling kept the ketone at the C4-position of LPMO oxidized oligosaccharides intact, while selective reducing agents such as sodium triacetoxyborohydride (STAB) reduced this ketone group. Our results show that RP-UHPLC-UV-ESI-MS in combination with non-reductively 2-AB labeling is a suitable technique for the separation and identification of LPMO-generated C4-oxidized gluco-oligosaccharides.
Characterization of a novel theme C glycoside hydrolase family 9 cellulase and its CBM-chimeric enzymes.
Duan, C. J., Huang, M. Y., Pang, H., Zhao, J., Wu, C. X. & Feng, J. X. (2017). Applied Microbiology and Biotechnology, 1-15.
In bacterial cellulase systems, glycoside hydrolase family 9 (GH9) cellulases are generally regarded as the major cellulose-degrading factors besides GH48 exoglucanase. In this study, umcel9A, which was cloned from uncultured microorganisms from compost, with the encoded protein being theme C GH9 cellulase, was heterologously expressed in Escherichia coli, and the biochemical properties of the purified enzyme were characterized. Hydrolysis of carboxylmethylcellulose (CMC) by Umcel9A led to the decreased viscosity of CMC solution and production of reducing sugars. Interestingly, cellobiose was the major product when cellulosic materials were hydrolyzed by Umcel9A. Six representative carbohydrate-binding modules (CBMs) from different CBM families (CBM1, CBM2, CBM3, CBM4, CBM10, and CBM72) were fused with Umcel9A at the natural terminal position, resulting in significant enhancement of the binding capacity of the chimeric enzymes toward four different insoluble celluloses as compared with that of Umcel9A. Catalytic activity of the chimeric enzymes against insoluble celluloses, including phosphoric acid-swollen cellulose (PASC), alkali-pretreated sugarcane bagasse (ASB), filter paper powder (FPP), and Avicel, was higher than that of Umcel9A, except for Umcel9A-CBM3. In these chimeric enzymes, CBM4-Umcel9A exhibited the highest activity toward the four tested insoluble celluloses and displayed 4.2-, 3.0-, 2.4-, and 6.6-fold enhanced activity toward PASC, ASB, FPP, and Avicel, respectively, when compared with that of Umcel9A. CBM4-Umcel9A also showed highest Vmax and catalytic efficiency (kcat/KM) against PASC. Construction of chimeric enzymes may have potential applications in biocatalytic processes and provides insight into the evolution of the molecular architecture of catalytic module and CBM in GH9 cellulases.
Hexagonal Boron Nitride for Adsorption of Saccharides.
Kobayashi, H. & Fukuoka, A. (2017). The Journal of Physical Chemistry C.
Recognition of saccharides is crucial in their separation, purification, and catalytic conversion. In this work, we demonstrated that hexagonal boron nitride (h-BN) adsorbs saccharides in water. Controlled experiments and density functional theory calculations have indicated that the adsorption is mainly driven by dispersion force occurring between CH groups of saccharides and π electrons on basal plane of h-BN. Accordingly, h-BN can distinguish between different saccharides by the number of CH groups that can contact with the basal plane. The salt effect on the adsorption correlated with the Hofmeister series, which shows the presence of hydrophobic interactions in the adsorption of sugars. Moreover, conversion of glucose to fructose is accelerated by h-BN, possibly due to its acid/base catalysis.
Biochemical and biophysical properties of a metagenome-derived GH5 endoglucanase displaying an unconventional domain architecture.
Pimentel, A. C., Ematsu, G. C., Liberato, M. V., Paixão, D. A., Cairo, J. P. L. F., Mandelli, F., Tramontina, R., Gandin, C. A., Oliveira, N., Squina, F. M. & Alvarez, T. M. (2017). International Journal of Biological Macromolecules, 99, 384-393.
Endoglucanases are key enzymes in the degradation of cellulose, the most abundant polymer on Earth. The aim of this work was to perform the biochemical and biophysical characterization of CelE2, a soil metagenome derived endoglucanase. CelE2 harbors a conserved domain from glycoside hydrolase family 5 (GH5) and a C-terminal domain with identity to Calx-beta domains. The recombinant CelE2 displayed preference for hydrolysis of oat beta-glucan, followed by lichenan and carboxymethyl cellulose. Optimum values of enzymatic activity were observed at 45°C and pH 5.3, and CelE2 exhibited considerable thermal stability at 40°C for up to 360 min. Regarding the cleavage pattern on polysaccharides, the release of oligosaccharides with a wide degree of polymerization indicated a characteristic of endoglucanase activity. Furthermore, the analysis of products generated from the cleavage of cellooligosaccharides suggested that CelE2 exhibited transglycosylation activity. Interestingly, the presence of CaCl2 positively affect CelE2, including in the presence of surfactants. SAXS experiments provided key information on the effect of CaCl2 on the stability of CelE2 and dummy atom and rigid-body models were generated. To the best of our knowledge this is the first biochemical and biophysical characterization of an endoglucanase from family GH5 displaying this unconventional modular organization.