Thermostable sites and catalytic characterization of xylanase XYNB of Aspergillus niger SCTCC 400264

Abstract

In order to improve the expression of heat-resistant xylanase XYNB from Aspergillus niger SCTCC 400264, XynB has been cloned into Pichia pastoris secretary vector pPIC9K. The XynB production of recombinant P. pastoris was four times that of E. coli, and the Vmax and specific activity of XynB reached 2,547.7 μmol/mg and 4,757 U/mg, respectively. XynB still had 74% residual enzyme activity after 30 min of heat treatment at 80°C. From the van der Waals force analysis of XYNB (ACN89393 and AAS67299), there is one more oxygen radical in AAS67299 in their catalytic site, indicating that the local cavity is much more free, and it is more optimal for substrate binding, affinity reaction, and proton transfer, etc, and e ventually i ncreasing enzyme activity. The H-bonds analysis of XYNB indicated that there are two more H-bonds in the 33rd Ser of XYNB (AAS67299) than in the 33rd Ala(ACN89393), and two H-bonds between Ser70 and Asp67. © 2014 by The Korean Society for Microbiology and Biotechnology.