title: Expression of A. niger US368 xylanase in E. coli: purification, characterization and copper activation.
abstract: The XAn11 cDNA was cloned in pET-28a(+) and the recombinant plasmid was transformed in Escherichia coli. The His-tagged r-XAn11 was purified using Ni-NTA affinity and anion exchange chromatography. The enzyme showed a specific activity of 415.1 U mg(-1) and a molecular mass of 25 kDa. It had an optimal activity at pH 5 and 50°C. It was stable in a wide range of pH and in the presence of some detergents and organic solvents. In the presence of 3mM Cu2+, the relative activity of the His-tagged r-XAn11 was enhanced by 54%. This is the first work reporting that copper is a strong activator for xylanase activity making this enzyme very attractive for future industrial applications. Molecular modeling suggests that the contact region between the catalytic site and the N-terminal His-tag fusion peptide could be responsible for the different behavior of the native and recombinant enzyme toward copper.
authors.affiliation: Laboratoire de Microorganismes et de Biomolécules (LMB), Centre de Biotechnologie de Sfax (CBS), Université de Sfax, Route de Sidi Mansour Km 6, BP "1177" 3018 Sfax, Tunisia.
authors.forename: Fatma
authors.initials: F
authors.lastname: Elgharbi
authors.affiliation: Laboratoire de Microorganismes et de Biomolécules (LMB), Centre de Biotechnologie de Sfax (CBS), Université de Sfax, Route de Sidi Mansour Km 6, BP "1177" 3018 Sfax, Tunisia.
authors.forename: Hajer Ben
authors.initials: HB
authors.lastname: Hlima
authors.affiliation: Laboratoire de Microorganismes et de Biomolécules (LMB), Centre de Biotechnologie de Sfax (CBS), Université de Sfax, Route de Sidi Mansour Km 6, BP "1177" 3018 Sfax, Tunisia.
authors.forename: Ameny
authors.initials: A
authors.lastname: Farhat-Khemakhem
authors.affiliation: Laboratoire de Microorganismes et de Biomolécules (LMB), Centre de Biotechnologie de Sfax (CBS), Université de Sfax, Route de Sidi Mansour Km 6, BP "1177" 3018 Sfax, Tunisia.
authors.forename: Dorra
authors.initials: D
authors.lastname: Ayadi-Zouari
authors.affiliation: Laboratoire de Microorganismes et de Biomolécules (LMB), Centre de Biotechnologie de Sfax (CBS), Université de Sfax, Route de Sidi Mansour Km 6, BP "1177" 3018 Sfax, Tunisia. Electronic address: samir.bejar@cbs.rnrt.tn.
authors.forename: Samir
authors.initials: S
authors.lastname: Bejar
authors.affiliation: Laboratoire de Microorganismes et de Biomolécules (LMB), Centre de Biotechnologie de Sfax (CBS), Université de Sfax, Route de Sidi Mansour Km 6, BP "1177" 3018 Sfax, Tunisia.
authors.forename: Aïda
authors.initials: A
authors.lastname: Hmida-Sayari
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics*; D003001:Cloning, Molecular; D003300:Copper / Q000378:metabolism; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics*; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008958:Models, Molecular; D011134:Polysaccharides / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins; D013379:Substrate Specificity; D013696:Temperature; D014995:Xylosidases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D011134:Polysaccharides; D011993:Recombinant Fusion Proteins; D003300:Copper; D014995:Xylosidases
keywords: Aspergillus niger US368; Copper; Escherichia coli BL21; Expression; Gene cloning; Xylanase