Biotechnologically Relevant Enzymes and Proteins

Applied Microbiology and Biotechnology

, Volume 74, Issue 2, pp 339-346

First online:

Molecular cloning and heterologous expression of a new xylanase gene from Plectosphaerella cucumerina

  • Gui Min ZhangAffiliated withCollege of Life Science, Hubei UniversityState Key Laboratory of Agriculture Microorganism, Huazhong Agriculture University
  • , Jun HuangAffiliated withCollege of Life Science, Hubei University
  • , Guang Rui HuangAffiliated withCollege of Life Science, Hubei University
  • , Li Xin MaAffiliated withCollege of Life Science, Hubei University Email author 
  • , Xian En ZhangAffiliated withState Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences Email author 

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A gene encoding a new xylanase, named xynZG, was cloned by the genome-walking PCR method from the nematophagous fungus Plectosphaerella cucumerina. The genomic DNA sequence of xynZG contains a 780 bp open reading frame separated by two introns with the sizes of 50 and 46 bp. To our knowledge, this would be the first functional gene cloned from P. cucumerina. The 684 bp cDNA was cloned into vector pHBM905B and transformed into Pichia pastoris GS115 to select xylanase-secreting transformants on RBB-xylan containing plate. The optimal secreting time was 3 days at 25°C and enzymatic activities in the culture supernatants reached the maximum level of 362 U ml−1. The molecular mass of the enzyme was estimated to be 19 kDa on SDS-PAGE. The optimal pH and temperature of the purified enzyme is 6 and 40°C, respectively. The purified enzyme is stable at room temperature for at least 10 h. The K m and V max values for birchwood xylan are 2.06 mg ml−1 and 0.49 mmol min−1mg−1, respectively. The inhibitory effects of various mental ions were investigated. It is interesting to note that Cu2+ ion, which strongly inhibits most other xylanases studied, reduces enzyme activity by only 40%. Furthermore, enzyme activity is unaffected by EDTA even at a concentration of 5 mM.


Xylanase Plectosphaerella cucumerina Genome-walking PCR Heterologous expression Pichia pastoris