title: A new acidophilic endo-β-1,4-xylanase from Penicillium oxalicum: cloning, purification, and insights into the influence of metal ions on xylanase activity.
abstract: A new acidophilic xylanase (XYN11A) from Penicillium oxalicum GZ-2 has been purified, identified and characterized. Synchronized fluorescence spectroscopy was used for the first time to evaluate the influence of metal ions on xylanase activity. The purified enzyme was identified by MALDI TOF/TOF mass spectrometry, and its gene (xyn11A) was identified as an open reading frame of 706 bp with a 68 bp intron. This gene encodes a mature protein of 196 residues with a predicted molecular weight of 21.3 kDa that has the 100 % identity with the putative xylanase from the P. oxalicum 114-2. The enzyme shows a structure comprising a catalytic module family 10 (GH10) and no carbohydrate-binding module family. The specific activities were 150.2, 60.2, and 72.6 U/mg for beechwood xylan, birchwood xylan, and oat spelt xylan, respectively. XYN11A exhibited optimal activity at pH 4.0 and remarkable pH stability under extremely acidic condition (pH 3). The specific activity, K m and V max values were 150.2 U/mg, 30.7 mg/mL, and 403.9 μmol/min/mg for beechwood xylan, respectively. XYN11A is a endo-β-1,4-xylanase since it release xylobiose and xylotriose as the main products by hydrolyzing xylans. The activity of XYN11A was enhanced 155 % by 1 mM Fe(2+) ions, but was inhibited strongly by Fe(3+). The reason of enhancing the xylanase activity of XYN11A with 1 mM Fe(2+) treatment may be responsible for the change of microenvironment of tryptophan residues studied by synchronous fluorescence spectrophotometry. Inhibition of the xylanase activity by Fe(3+) was first time demonstrated to associate tryptophan fluorescence quenching.
authors.affiliation: Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Hanpeng
authors.initials: H
authors.lastname: Liao
authors.forename: Shaowei
authors.initials: S
authors.lastname: Sun
authors.forename: Pan
authors.initials: P
authors.lastname: Wang
authors.forename: Wenli
authors.initials: W
authors.lastname: Bi
authors.forename: Shiyong
authors.initials: S
authors.lastname: Tan
authors.forename: Zhong
authors.initials: Z
authors.lastname: Wei
authors.forename: Xinlan
authors.initials: X
authors.lastname: Mei
authors.forename: Dongyang
authors.initials: D
authors.lastname: Liu
authors.forename: Waseem
authors.initials: W
authors.lastname: Raza
authors.forename: Qirong
authors.initials: Q
authors.lastname: Shen
authors.forename: Yangchun
authors.initials: Y
authors.lastname: Xu
mesh_terms: D000595:Amino Acid Sequence; D001709:Biotechnology; D003001:Cloning, Molecular; D043364:Endo-1,4-beta Xylanases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis / Q000187:drug effects; D007700:Kinetics; D008670:Metals / Q000378:metabolism / Q000494:pharmacology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010407:Penicillium / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity; D013696:Temperature; D014364:Tryptophan / Q000378:metabolism; D014990:Xylans / Q000378:metabolism
chemical_list: D008670:Metals; D014990:Xylans; D014364:Tryptophan; D043364:Endo-1,4-beta Xylanases