title: Purification and biochemical characterization of a highly thermostable xylanase from Actinomadura sp. strain Cpt20 isolated from poultry compost.
abstract: An extracellular thermostable xylanase from a newly isolated thermophilic Actinomadura sp. strain Cpt20 was purified and characterized. Based on matrix-assisted laser desorption-ionization time-of-flight mass spectrometry analysis, the purified enzyme is a monomer with a molecular mass of 20,110.13 Da. The 19 residue N-terminal sequence of the enzyme showed 84% homology with those of actinomycete endoxylanases. The optimum pH and temperature values for xylanase activity were pH 10 and 80 °C, respectively. This xylanase was stable within a pH range of 5-10 and up to a temperature of 90 °C. It showed high thermostability at 60 °C for 5 days and half-life times at 90 °C and 100 °C were 2 and 1 h, respectively. The xylanase was specific for xylans, showing higher specific activity on soluble oat-spelt xylan followed by beechwood xylan. This enzyme obeyed the Michaelis-Menten kinetics, with the K (m) and k (cat) values being 1.55 mg soluble oat-spelt xylan/ml and 388 min(-1), respectively. While the xylanase from Actinomadura sp. Cpt20 was activated by Mn(2+), Ca(2+), and Cu(2+), it was, strongly inhibited by Hg(2+), Zn(2+), and Ba(2+). These properties make this enzyme a potential candidate for future use in biotechnological applications particularly in the pulp and paper industry.
authors.affiliation: Laboratory of Applied Biochemistry and Microbiology, Faculty of Science of Annaba, Badji Mokhtar-Annaba University, P.O. Box 12, 23000 Annaba, Algeria.
authors.forename: Zina
authors.initials: Z
authors.lastname: Taibi
authors.forename: Boudjemaa
authors.initials: B
authors.lastname: Saoudi
authors.forename: Mokhtar
authors.initials: M
authors.lastname: Boudelaa
authors.forename: Héla
authors.initials: H
authors.lastname: Trigui
authors.forename: Hafedh
authors.initials: H
authors.lastname: Belghith
authors.forename: Ali
authors.initials: A
authors.lastname: Gargouri
authors.forename: Ali
authors.initials: A
authors.lastname: Ladjama
mesh_terms: D000192:Actinomycetales / Q000737:chemistry / Q000201:enzymology*; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D002645:Chickens; D043364:Endo-1,4-beta Xylanases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D004795:Enzyme Stability; D006207:Half-Life; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010802:Phylogeny; D011200:Poultry; D012336:RNA, Ribosomal, 16S / Q000096:biosynthesis*; D012987:Soil; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity; D014990:Xylans / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; D012987:Soil; D014990:Xylans; D043364:Endo-1,4-beta Xylanases