scholarly journals A Novel Dimeric Exoglucanase (GH5_38): Biochemical and Structural Characterisation towards its Application in Alkyl Cellobioside Synthesis

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 746 ◽  
Author(s):  
Mpho S. Mafa ◽  
Heinrich W. Dirr ◽  
Samkelo Malgas ◽  
Rui W. M. Krause ◽  
Konanani Rashamuse ◽  
...  
Keyword(s):  
Glycoside Hydrolase ◽  
Kinetic Studies ◽  
Glycoside Hydrolase Family ◽  
Primary Alcohols ◽  
Structural Characterisation ◽  
Alkyl Glycosides ◽  
Glycoside Synthesis ◽  
One Step ◽  
Ph Range ◽  
The One

An exoglucanase (Exg-D) from the glycoside hydrolase family 5 subfamily 38 (GH5_38) was heterologously expressed and structurally and biochemically characterised at a molecular level for its application in alkyl glycoside synthesis. The purified Exg-D existed in both dimeric and monomeric forms in solution, which showed highest activity on mixed-linked β-glucan (88.0 and 86.7 U/mg protein, respectively) and lichenin (24.5 and 23.7 U/mg protein, respectively). They displayed a broad optimum pH range from 5.5 to 7 and a temperature optimum from 40 to 60 °C. Kinetic studies demonstrated that Exg-D had a higher affinity towards β-glucan, with a Km of 7.9 mg/mL and a kcat of 117.2 s−1, compared to lichenin which had a Km of 21.5 mg/mL and a kcat of 70.0 s−1. The circular dichroism profile of Exg-D showed that its secondary structure consisted of 11% α-helices, 36% β-strands and 53% coils. Exg-D performed transglycosylation using p-nitrophenyl cellobioside as a glycosyl donor and several primary alcohols as acceptors to produce methyl-, ethyl- and propyl-cellobiosides. These products were identified and quantified via thin-layer chromatography (TLC) and liquid chromatography–mass spectrometry (LC-MS). We concluded that Exg-D is a novel and promising oligomeric glycoside hydrolase for the one-step synthesis of alkyl glycosides with more than one monosaccharide unit.

scholarly journals Novel pH-Stable Glycoside Hydrolase Family 3 β-Xylosidase from Talaromyces amestolkiae: an Enzyme Displaying Regioselective Transxylosylation

2015 ◽  
Vol 81 (18) ◽  
pp. 6380-6392 ◽  
Author(s):  
Manuel Nieto-Domínguez ◽  
Laura I. de Eugenio ◽  
Jorge Barriuso ◽  
Alicia Prieto ◽  
Beatriz Fernández de Toro ◽  
...  
Keyword(s):  
Glycoside Hydrolase ◽  
Glycoside Hydrolase Family ◽  
Gene Encoding ◽  
Intronless Gene ◽  
Content Type ◽  
Alkyl Glycosides ◽  
Beechwood Xylan ◽  
Dimeric Form ◽  
Culture Supernatants ◽  
Hydrolysis Of

ABSTRACTThis paper reports on a novel β-xylosidase from the hemicellulolytic fungusTalaromyces amestolkiae. The expression of this enzyme, called BxTW1, could be induced by beechwood xylan and was purified as a glycoprotein from culture supernatants. We characterized the gene encoding this enzyme as an intronless gene belonging to the glycoside hydrolase gene family 3 (GH3). BxTW1 exhibited transxylosylation activity in a regioselective way. This feature would allow the synthesis of oligosaccharides or other compounds not available from natural sources, such as alkyl glycosides displaying antimicrobial or surfactant properties. Regioselective transxylosylation, an uncommon combination, makes the synthesis reproducible, which is desirable for its potential industrial application. BxTW1 showed high pH stability and Cu2+tolerance. The enzyme displayed a pI of 7.6, a molecular mass around 200 kDa in its active dimeric form, andKmandVmaxvalues of 0.17 mM and 52.0 U/mg, respectively, using commercialp-nitrophenyl-β-d-xylopyranoside as the substrate. The catalytic efficiencies for the hydrolysis of xylooligosaccharides were remarkably high, making it suitable for different applications in food and bioenergy industries.

Overproduction and characterization of xylanase B fromAspergillus niger

2005 ◽  
Vol 51 (2) ◽  
pp. 177-183 ◽  
Author(s):  
Anthony Levasseur ◽  
Marcel Asther ◽  
Eric Record
Keyword(s):  
Expression System ◽  
Gene Promoter ◽  
Recombinant Enzyme ◽  
Glycoside Hydrolase Family ◽  
Metal Affinity ◽  
Homologous Expression ◽  
Dehydrogenase Gene ◽  
Beet Pulp ◽  
One Step ◽  
Ph Range

The xynB gene, which encodes endo-β-1,4-xylanase XynB, in Aspergillus niger BRFM281 was amplified by RT-PCR using mRNA isolated from a culture containing sugar beet pulp as an inducer. The cDNA was cloned into an expression cassette under the control of the strong and constitutive glyceraldhehyde-3-phosphate dehydrogenase gene promoter. The expression system was designed to produce the recombinant enzyme XynB with a six-histidine peptide fused to the carboxy end of the protein. Homologous overproduction of XynB was successfully achieved in shake flask cultures, and the secretion yield was estimated to be 900 mg·L–1. The recombinant XynB was purified 1.5-fold by immobilized metal affinity chromatography to homogeneity using a one-step purification protocol with 71% recovery. The purified recombinant enzyme was fully characterized and has a molecular mass of 23 kDa and an optimal activity at pH 5.5 and 50 °C with stability in the pH range 4.0-7.0 and temperature up to 50 °C. Using soluble oat spelts xylan, the determined Kmand Vmaxvalues were 7.1 mg·mL–1and 3881 U·mg–1, respectively.Key words: homologous expression, glycoside hydrolase family 11, cell-wall degradation.

scholarly journals Biological Characteristics and Genomic Analysis of Aeromonas Hydrophila Phage BUCT551 Isolated From Aquatic Sewage

2021 ◽  
Author(s):  
Hongbo Qin ◽  
Shiting He ◽  
Xuling Xu ◽  
Xiaoping An ◽  
Ke Liu ◽  
...  
Keyword(s):  
Aeromonas Hydrophila ◽  
Burst Size ◽  
Genomic Analysis ◽  
Opportunistic Pathogen ◽  
Range Analysis ◽  
Transmission Electron ◽  
Blastn Analysis ◽  
One Step ◽  
Ph Range ◽  
The One

Abstract Aeromonas hydrophila is a common opportunistic pathogen in aquaculture and is ubiquitous in aquatic environment. Whereby its accessibility, variety and host specificity, phage is increasingly considered as a promising complementary medicine for antibiotics. However, a small amount of A. hydrophila phages have been characterized, which suggests the significance to isolate and characterize novel A. hydrophila phages. In this study, we isolated a novel Aeromonas hydrophila phage using A. hydrophila strain A18 as an indicator and designated it as BUCT551, and it was identified as Myoviridae phage by transmission electron microscopy (TEM). The whole genome sequencing of the phage BUCT551 revealed that it has a linear DNA genome of 613,82 bp. BLASTn analysis showed that phage BUCT551 shared 86.75% homology with A. hydrophila phage LAh_7 (Genebank ID: MK838113.1). The one-step growth curve demonstrated that phage BUCT551 had a latent period of 20 min and the burst size of 32 pfu/cell at its optimal MOI of 0.1. The phage BUCT551 had a survival pH range from 5 to 10 and tolerant temperature from 0℃ to 40℃. Host range analysis shown that the phage was able to lyse not only A. hydrophila, but also A. veronii.

Targeted Synthesis of Nanostructured Oxide Materials

2007 ◽  
Vol 1056 ◽  
Author(s):  
Greta Ricarda Patzke ◽  
Ying Zhou
Keyword(s):  
Hydrothermal Process ◽  
Kinetic Studies ◽  
Complex Oxide ◽  
Morphology Control ◽  
Oxide Materials ◽  
New Materials ◽  
Binary Oxides ◽  
Nanostructured Oxide ◽  
One Step ◽  
The One

ABSTRACTMorphology control is a key challenge in the straightforward hydrothermal production of technologically relevant anisotropic oxide materials. The use of readily available ionic additives as growth modifiers is discussed and compared for molybdenum- and tungsten oxide-based systems, and it is extended upon the formation of ternary W/Mo-oxides. Generally, the one-step hydrothermal synthesis of ternary and higher oxides is an important goal, because their properties often outperform those of the binary oxides. This holds especially for the Bi2O3-MoO3-VOx (BIMOVOx) system as a rich source of new materials. We present a new solution-based approach to α-Bi2O3 nanobelts starting from commercial Bi2O3 and K2SO4 as a key step on the way to anisotropic BIMOVOx-oxides. This hydrothermal process is an illustrative example of highly selective and efficient morphology control through an inorganic additive. As mechanistic and kinetic studies are crucial for the design of complex oxide nanomaterials, the Bi2O3-K2SO4 system is compared to our previous studies on Mo-, W- and V-oxides with respect to its hydrothermal parameter window and robustness.

pH-Dependent Thermal Stability of Vibrio cholerae L-asparaginase

2019 ◽  
Vol 26 (10) ◽  
pp. 743-750 ◽  
Author(s):  
Remya Radha ◽  
Sathyanarayana N. Gummadi
Keyword(s):  
Vibrio Cholerae ◽  
Conformational Changes ◽  
Kinetic Studies ◽  
Structural Features ◽  
Structure Stability ◽  
Kcal Mole ◽  
Scanning Calorimetry ◽  
Wide Range ◽  
Ph Dependent ◽  
Ph Range

Background:pH is one of the decisive macromolecular properties of proteins that significantly affects enzyme structure, stability and reaction rate. Change in pH may protonate or deprotonate the side group of aminoacid residues in the protein, thereby resulting in changes in chemical and structural features. Hence studies on the kinetics of enzyme deactivation by pH are important for assessing the bio-functionality of industrial enzymes. L-asparaginase is one such important enzyme that has potent applications in cancer therapy and food industry.Objective:The objective of the study is to understand and analyze the influence of pH on deactivation and stability of Vibrio cholerae L-asparaginase.Methods:Kinetic studies were conducted to analyze the effect of pH on stability and deactivation of Vibrio cholerae L-asparaginase. Circular Dichroism (CD) and Differential Scanning Calorimetry (DSC) studies have been carried out to understand the pH-dependent conformational changes in the secondary structure of V. cholerae L-asparaginase.Results:The enzyme was found to be least stable at extreme acidic conditions (pH< 4.5) and exhibited a gradual increase in melting temperature from 40 to 81 °C within pH range of 4.0 to 7.0. Thermodynamic properties of protein were estimated and at pH 7.0 the protein exhibited ΔG37of 26.31 kcal mole-1, ΔH of 204.27 kcal mole-1 and ΔS of 574.06 cal mole-1 K-1.Conclusion:The stability and thermodynamic analysis revealed that V. cholerae L-asparaginase was highly stable over a wide range of pH, with the highest stability in the pH range of 5.0–7.0.

A Study on the Rearrangement of Dialkyl 1-Aryl-1-hydroxymethylphosphonates to Benzyl Phosphates

2020 ◽  
Vol 24 (4) ◽  
pp. 465-471 ◽  
Author(s):  
Zita Rádai ◽  
Réka Szabó ◽  
Áron Szigetvári ◽  
Nóra Zsuzsa Kiss ◽  
Zoltán Mucsi ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Room Temperature ◽  
Phase Transfer ◽  
One Pot ◽  
Substrate Dependence ◽  
Triethylbenzylammonium Chloride ◽  
One Step ◽  
The Pudovik Reaction ◽  
The One ◽  
Solid Liquid

The phospha-Brook rearrangement of dialkyl 1-aryl-1-hydroxymethylphosphonates (HPs) to the corresponding benzyl phosphates (BPs) has been elaborated under solid-liquid phase transfer catalytic conditions. The best procedure involved the use of triethylbenzylammonium chloride as the catalyst and Cs2CO3 as the base in acetonitrile as the solvent at room temperature. The substrate dependence of the rearrangement has been studied, and the mechanism of the transformation under discussion was explored by quantum chemical calculations. The key intermediate is an oxaphosphirane. The one-pot version starting with the Pudovik reaction has also been developed. The conditions of this tandem transformation were the same, as those for the one-step HP→BP conversion.

Efficient Preconcentration of Cu2+, Zn2+ and Fe3+ with an Agarose-Schiff Base Sorbent

2007 ◽  
Vol 72 (7) ◽  
pp. 908-916 ◽  
Author(s):  
Payman Hashemi ◽  
Hatam Hassanvand ◽  
Hossain Naeimi
Keyword(s):  
Schiff Base ◽  
Metal Ions ◽  
Metal Ion ◽  
Good Accuracy ◽  
Kinetic Studies ◽  
Sample Volume ◽  
Effects Of Ph ◽  
Glass Column ◽  
High Concentrations ◽  
Ph Range

Sorption and preconcentration of Cu2+, Zn2+ and Fe3+ on a salen-type Schiff base, 2,2'- [ethane-1,2-diylbis(nitrilomethylidyne)]bis(2-methylphenol), chemically immobilized on a highly crosslinked agarose support, were studied. Kinetic studies showed higher sorption rates of Cu2+ and Fe3+ in comparison with Zn2+. Half-times (t1/2) of 31, 106 and 58 s were obtained for sorption of Cu2+, Zn2+ and Fe3+ by the sorbent, respectively. Effects of pH, eluent concentration and volume, ionic strength, buffer concentration, sample volume and interferences on the recovery of the metal ions were investigated. A 5-ml portion of 0.4 M HCl solution was sufficient for quantitative elution of the metal ions from 0.5 ml of the sorbent packed in a 6.5 mm i.d. glass column. Quantitative recoveries were obtained in a pH range 5.5-6.5 for all the analytes. The volumes to be concentrated exceeding 500 ml, ionic strengths as high as 0.5 mol l-1, and acetate buffer concentrations up to 0.3 mol l-1 for Zn2+ and 0.4 mol l-1 for Cu2+ and Fe3+ did not have any significant effect on the recoveries. The system tolerated relatively high concentrations of diverse ions. Preconcentration factors up to 100 and detection limits of 0.31, 0.16 and 1.73 μg l-1 were obtained for Cu2+, Zn2+ and Fe3+, respectively, for their determination by a flame AAS instrument. The method was successfully applied to the metal ion determinations in several river water samples with good accuracy.

Xylanases of glycoside hydrolase family 30 – An overview

2021 ◽  
Vol 47 ◽  
pp. 107704
Author(s):  
Vladimír Puchart ◽  
Katarína Šuchová ◽  
Peter Biely
Keyword(s):  
Glycoside Hydrolase ◽  
Glycoside Hydrolase Family ◽  
Hydrolase Family ◽  
Glycoside Hydrolase Family 30

scholarly journals One-Year Clinical Evaluation of the Bonding Effectiveness of a One-Step, Self-Etch Adhesive in Noncarious Cervical Lesion Therapy

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Babacar Faye ◽  
Mouhamed Sarr ◽  
Khaly Bane ◽  
Adjaratou Wakha Aidara ◽  
Seydina Ousmane Niang ◽  
...  
Keyword(s):  
Clinical Performance ◽  
Retention Rate ◽  
Recall Rate ◽  
Acid Etching ◽  
Significant Difference ◽  
Usphs Criteria ◽  
One Step ◽  
One Year ◽  
The One ◽  
Self Etch

This study evaluated the one-year clinical performance of a one-step, self-etch adhesive (Optibond All-in-One, Kerr, CA, USA) combined with a composite (Herculite XRV Ultra, Kerr Hawe, CA, USA) to restore NCCLs with or without prior acid etching. Restorations performed by the same practitioner were evaluated at baseline and after 3, 6, and 12 months using modified USPHS criteria. At 6 months, the recall rate was 100%. The retention rate was 84.2% for restorations with prior acid etching, but statistically significant differences were observed between baseline and 6 months. Without acid etching, the retention rate was 77%, and no statistically significant difference was noted between 3 and 6 months. Marginal integrity (93.7% with and 87.7% without acid etching) and discoloration (95.3% with and 92.9% without acid etching) were scored as Alpha or Bravo, with better results after acid etching. After one year, the recall rate was 58.06%. Loss of pulp vitality, postoperative sensitivity, or secondary caries were not observed. After one year retention rate was of 90.6% and 76.9% with and without acid conditioning. Optibond All-in-One performs at a satisfactory clinical performance level for restoration of NCCLs after 12 months especially after acid etching.

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