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|Formulation:||In 3.2 M ammonium sulphate|
|Stability:||Minimum 1 year at 4oC. Check vial for details.|
|Synonyms:||xylan 1,4-beta-xylosidase; 4-beta-D-xylan xylohydrolase|
|Concentration:||Supplied at ~ 75 U/mL|
|Expression:||Recombinant from Bacillus pumilus|
|Specificity:||Hydrolysis of (1,4)-β-D-xylans and xylo-oligosaccharides to remove successive D-xylose residues from non-reducing termini.|
|Specific Activity:||~ 18 U/mg (35oC, pH 7.5 on p-nitrophenyl-β-D-xylopyranoside)|
|Unit Definition:||One Unit of β-xylosidase activity is defined as the amount of enzyme required to release one µmole of p-nitrophenol (pNP) per minute from p-nitrophenyl-β-Dxylopyranoside (5 mM) in potassium phosphate buffer (50 mM), pH 7.5 at 35oC.|
|Application examples:||Applications in carbohydrate and biofuels research.|
Aroma enhancement of instant green tea infusion using β-glucosidase and β-xylosidase.
Zhang, T., Fang, K., Ni, H., Li, T., Li, L. J., Li, Q. B. & Chen, F. (2020). Food Chemistry, 315, 126287.
β-Glucosidase and β-xylosidase were investigated for their ability to improve the aroma of instant green tea. The aroma and corresponding contributors were analyzed by sensory evaluation, gas chromatography-mass spectrometry, and odor activity value. Their specific contributions to aroma attributes were further examined by aroma reconstruction and omission experiments. The β-glucosidase treatment significantly enhanced floral and grassy notes, on account of the increases of geraniol, nonanal, and cis-3-hexen-1-ol, and weakened the caramel note, attributable to the increases of nonanal, cis-3-hexen-1-ol, geraniol, methyl salicylate, and decanal. The co-treatment with β-glucosidase and β-xylosidase further enhanced the grassy note, with further increase in nonanal and cis-3-hexen-1-ol, and further weakened the caramel note, with additional increase in nonanal, cis-3-hexen-1-ol, methyl salicylate, and decanal. The synergistic action of β-glucosidase and β-xylosidase provides new clues to the production of instant green tea infusions with high aroma quality.Hide Abstract
Highly Efficient Degradation of Xylan into Xylose by a Single Enzyme.
Basit, A., Miao, T., Liu, J., Wen, J., Song, L., Zheng, F., Lou, H. & Jiang, W. (2019). ACS Sustainable Chemistry & Engineering, 7(13), 11360-11368.
Here, we report highly efficient degradation of xylan into xylose by a single multifunctional xylanolytic enzyme from the filamentous fungus Thermothelomyces thermophila (termed Ttxy43). Ttxy43 shows three different enzyme activities toward carbohydrates, β-xylosidase (80.8 U/mg), endoxylanase (105.42 U/mg), and α-l-arabinofuranosidase enzyme activities (15.81 U/mg). Analysis of the catalytic mode of action of Ttxy43 for birchwood-xylan (BWX) reveals that endoxylanase initially degrades xylan to unbranched xylooligosaccharides (XOSs) (xylobiose, xylotriose, xylotetraose) as intermediates, which are then quickly hydrolyzed into single xylose by β-xylosidase. Site-directed mutagenesis studies indicate that Ttxy43 residues Asp134 and Glu228 are essential catalytic sites, while Glu176, Asp38, and Asp85 play an accessory role. More importantly, Ttxy43 displays higher degradation efficiency in comparison with a commercial β-xylosidase and endoxylanase “cocktail”. These findings elucidate an efficient integrated degradation mechanism of xylan under industrial reaction conditions, which provides a novel strategy to design techniques for biomass energy production.Hide Abstract
Smoke from simulated forest fire alters secondary metabolites in Vitis vinifera L. berries and wine.
Noestheden, M., Noyovitz, B., Riordan-Short, S., Dennis, E. G. & Zandberg, W. F. (2018). Planta, 248(6), 1537-1550.
The exposure of Vitis vinifera L. berries to forest fire smoke changes the concentration of phenylpropanoid metabolites in berries and the resulting wine. The exposure of Vitis vinifera L. berries (i.e., wine grapes) to forest fire smoke can lead to a wine defect known as smoke taint that is characterized by unpleasant “smoky” and “ashy” aromas and flavors. The intensity of smoke taint is associated with the concentration of organoleptic volatile phenols that are produced during the combustion-mediated oxidation of lignocellulosic biomass and subsequently concentrated in berries prior to fermentation. However, these same smoke-derived volatile phenols are also produced via metabolic pathways endogenous to berries. It follows then that an influx of exogenous volatile phenols (i.e., from forest fire smoke) could alter endogenous metabolism associated with volatile phenol synthesis, which occurs via the shikimic acid/phenylpropanoid pathways. The presence of ozone and karrikins in forest fire smoke, as well as changes to stomatal conductance that can occur from exposure to forest fire smoke also have the potential to influence phenylpropanoid metabolism. This study demonstrated changes in phenylpropanoid metabolites in Pinot noir berries and wine from three vineyards following the exposure of Vitis vinifera L. vines to simulated forest fire smoke. This included changes to metabolites associated with mouth feel and color in wine, both of which are important sensorial qualities to wine producers and consumers. The results reported are critical to understanding the chemical changes associated with smoke taint beyond volatile phenols, which in turn, may aid the development of preventative and remedial strategies.Hide Abstract
Septiningrum, K., Ohi, H., Waeonukul, R., Pason, P., Tachaapaikoon, C., Ratanakhanokchai, K., Sermsathanaswadi, J., Deng, L., Prawitwong, P. & Kosugi, A. (2015). Enzyme and Microbial Technology, 71, 28-35.
4-O-Methylglucuronic acid (MeGlcA) side groups attached to the xylan backbone through α-1,2 linkages are converted to hexenuronic acid (HexA) during alkaline pulping. α-Glucuronidase (EC 220.127.116.11) hydrolyzes 1,2-linked MeGlcA from xylooligosaccharides. To determine whether α-glucuronidase can also hydrolyze HexA-decorated xylooligosaccharides, a gene encoding α-glucuronidase (AguA) was cloned from Paenibacillus curdlanolyticus B-6. The purified protein degraded hexenuronosyl xylotriose (ΔX3), a model substrate prepared from kraft pulp. AguA released xylotriose and HexA from ΔX3, but the Vmax and kcat values for ΔX3 were lower than those for MeGlcA, indicating that HexA side groups may affect the hydrolytic activity. To explore the potential for biological bleaching, ΔX3 degradation was performed using intracellular extract from P. curdlanolyticus B-6. The intracellular extract, with synergistic α-glucuronidase and β-xylosidase activities, degraded ΔX3 to xylose and HexA. These results indicate that α-glucuronidase can be used to remove HexA from ΔX3 derived from pulp, reducing the need for chemical treatments in the pulping process.Hide Abstract
Najah, M., Mayot, E., Mahendra-Wijaya, I. P., Griffiths, A. D., Ladame, S. & Drevelle, A. (2013). Analytical Chemistry, 85(20), 9807-9814.
Droplet-based microfluidics is a powerful technique allowing ultra-high-throughput screening of large libraries of enzymes or microorganisms for the selection of the most efficient variants. Most applications in droplet microfluidic screening systems use fluorogenic substrates to measure enzymatic activities with fluorescence readout. It is important, however, that there is little or no fluorophore exchange between droplets, a condition not met with most commonly employed substrates. Here we report the synthesis of fluorogenic substrates for glycosidases based on a sulfonated 7-hydroxycoumarin scaffold. We found that the presence of the sulfonate group effectively prevents leakage of the coumarin from droplets, no exchange of the sulfonated coumarins being detected over 24 h at 30°C. The fluorescence properties of these substrates were characterized over a wide pH range, and their specificity was studied on a panel of relevant glycosidases (cellulases and xylanases) in microtiter plates. Finally, the β-D-cellobioside-6,8-difluoro-7-hydroxycoumarin-4-methanesulfonate substrate was used to assay cellobiohydrolase activity on model bacterial strains (Escherichia coli and Bacillus subtilis) in a droplet-based microfluidic format. These new substrates can be used to assay glycosidase activities in a wide pH range (4–11) and with incubation times of up to 24 h in droplet-based microfluidic systems.Hide Abstract
Jordan, D. B., Wagschal, K., Grigorescu, A. A. & Braker, J. D. (2013). Applied Microbiology and Biotechnology, 97(10), 4415-4428.
The hemicellulose xylan constitutes a major portion of plant biomass, a renewable feedstock available for conversion to biofuels and other bioproducts. β-xylosidase operates in the deconstruction of the polysaccharide to fermentable sugars. Glycoside hydrolase family 43 is recognized as a source of highly active β-xylosidases, some of which could have practical applications. The biochemical details of four GH43 β-xylosidases (those from Alkaliphilus metalliredigens QYMF, Bacillus pumilus, Bacillus subtilis subsp. subtilis str. 168, and Lactobacillus brevis ATCC 367) are examined here. Sedimentation equilibrium experiments indicate that the quaternary states of three of the enzymes are mixtures of monomers and homodimers (B. pumilus) or mixtures of homodimers and homotetramers (B. subtilis and L. brevis). k cat and k cat/k m values of the four enzymes are higher for xylobiose than for xylotriose, suggesting that the enzyme active sites comprise two subsites, as has been demonstrated by the X-ray structures of other GH43 β-xylosidases. The k i values for D-glucose (83.3–357 mM) and D-xylose (15.6–70.0 mM) of the four enzymes are moderately high. The four enzymes display good temperature (k t 0.5~~ 45°C) and pH stabilities (>4.6 to <10.3). At pH 6.0 and 25°C, the enzyme from L. brevis ATCC 367 displays the highest reported k cat and k cat/k m on natural substrates xylobiose (407 s-1, 138 s-1 mM-1), xylotriose (235 s-1, 80.8 s-1 mM-1), and xylotetraose (146 s-1, 32.6 s-1 mM-1).Hide Abstract
Franková, L. & Fry, S. C. (2012). Phytochemistry, 78, 29-43.
Angiosperms possess a retaining trans-α-xylosidase activity that catalyses the inter-molecular transfer of xylose residues between xyloglucan structures. To identify the linkage of the newly transferred α-xylose residue, we used [Xyl-3H]XXXG (xyloglucan heptasaccharide) as donor substrate and reductively-aminated xyloglucan oligosaccharides (XGO–NH2) as acceptor. Asparagus officinalis enzyme extracts generated cationic radioactive products ([3H]Xyl·XGO–NH2) that were Driselase-digestible to a neutral trisaccharide containing an α-[3H]xylose residue. After borohydride reduction, the trimer exhibited high molybdate-affinity, indicating xylobiosyl-(1→6)-glucitol rather than a di-xylosylated glucitol. Thus the trans-α-xylosidase had grafted an additional α-[3H]xylose residue onto the xylose of an isoprimeverose unit. The trisaccharide was rapidly acetolysed to an α-[3H]xylobiose, confirming the presence of an acetolysis-labile (1→6)-bond. The α-[3H]xylobiitol formed by reduction of this α-[3H]xylobiose had low molybdate-affinity, indicating a (1→2) or (1→4) linkage. In NaOH, the α-[3H]xylobiose underwent alkaline peeling at the moderate rate characteristic of a (1→4)-disaccharide. Finally, we synthesised eight non-radioactive xylobioses [α and β; (1↔1), (1→2), (1→3) and (1→4)] and found that the [3H]xylobiose co-chromatographed only with (1→4)-α-xylobiose. We conclude that Asparagus trans-α-xylosidase activity generates a novel xyloglucan building block, α-D-Xylp-(1→4)-α-D-Xylp-(1→6)-D-Glc (abbreviation: ‘V’). Modifying xyloglucan structures in this way may alter oligosaccharin activities, or change their suitability as acceptor substrates for xyloglucan endotransglucosylase (XET) activity.Hide Abstract
Franková, L. & Fry, S. C. (2012). The Plant Journal, 71(1), 45-60.
Cell-wall components are hydrolysed by numerous plant glycosidase and glycanase activities. We investigated whether plant enzymes also modify xyloglucan structures by transglycosidase activities. Diverse angiosperm extracts exhibited transglycosidase activities that progressively transferred single sugar residues between xyloglucan heptasaccharide (XXXG or its reduced form, XXXGol) molecules, at 16 µm and above, creating octa- to decasaccharides plus smaller products. We measured remarkably high transglycosylation:hydrolysis ratios under optimized conditions. To identify the transferred monosaccharide(s), we devised a dual-labelling strategy in which a neutral radiolabelled oligosaccharide (donor substrate) reacted with an amino-labelled non-radioactive oligosaccharide (acceptor substrate), generating radioactive cationic products. For example, 37 µm [Xyl-3H]XXXG plus 1 mm XXLG-NH2 generated 3H-labelled cations, demonstrating xylosyl transfer, which exceeded xylosyl hydrolysis 1.6- to 7.3-fold, implying the presence of enzymes that favour transglycosylation. The transferred xylose residues remained α-linked but were relatively resistant to hydrolysis by plant enzymes. Driselase digestion of the products released a trisaccharide (α-[3H]xylosyl-isoprimeverose), indicating that a new xyloglucan repeat unit had been formed. In similar assays, [Gal-3H]XXLG and [Gal-3H]XLLG (but not [Fuc-3H]XXFG) yielded radioactive cations. Thus plants exhibit trans-α-xylosidase and trans-β-galactosidase (but not trans-α-fucosidase) activities that graft sugar residues from one xyloglucan oligosaccharide to another. Reconstructing xyloglucan oligosaccharides in this way may alter oligosaccharin activities or increase their longevity in vivo. Trans-α-xylosidase activity also transferred xylose residues from xyloglucan oligosaccharides to long-chain hemicelluloses (xyloglucan, water-soluble cellulose acetate, mixed-linkage β-glucan, glucomannan and arabinoxylan). With xyloglucan as acceptor substrate, such an activity potentially affects the polysaccharide’s suitability as a substrate for xyloglucan endotransglucosylase action and thereby modulates cell expansion. We conclude that certain proteins annotated as glycosidases can function as transglycosidases.Hide Abstract