An acid and highly thermostable xylanase from Phialophora sp. G5.
An endo-β-1,4-xylanase gene, designated xyn10G5, was cloned from Phialophora sp. G5 and expressed in Pichia pastoris. The 1,197-bp full-length gene encodes a polypeptide of 399 amino acids consisting of a putative signal peptide at residues 1-20, a family 10 glycoside hydrolase domain, a short Gly/Thr-rich linker and a family 1 carbohydrate-binding module (CBM). The deduced amino acid sequence of XYN10G5 shares the highest identity (53.4%) with a putative xylanase precursor from Aspergillus terreus NIH2624. The purified recombinant XYN10G5 exhibited the optimal activity at pH 4.0 and 70 °C, remained stable at pH 3.0-9.0 (>70% of the maximal activity), and was highly thermostable at 70 °C (retaining ~90% of the initial activity for 1 h). Substrate specificity studies have shown that XYN10G5 had the highest activity on soluble wheat arabinoxylan (350.6 U mg(-1)), and moderate activity to various heteroxylans, and low activity on different types of cellulosic substrates. Under simulated gastric conditions, XYN10G5 was stable and released more reducing sugars from soluble wheat arabinoxylan; when combined with a glucanase (CelA4), the viscosity of barley-soybean feed was significantly reduced. These favorable enzymatic properties make XYN10G5 a good candidate for application in the animal feed industry.
Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, China.
Fan
F
Zhang
Pengjun
P
Shi
Yingguo
Y
Bai
Huiying
H
Luo
Tiezheng
T
Yuan
Huoqing
H
Huang
Peilong
P
Yang
Lihong
L
Miao
Bin
B
Yao
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D004795:Enzyme Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010676:Phialophora / Q000201:enzymology*; D010843:Pichia / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014990:Xylans / Q000378:metabolism
D004271:DNA, Fungal; D011994:Recombinant Proteins; D014990:Xylans; D043364:Endo-1,4-beta Xylanases