Characterization of a recombinant bifunctional xylosidase/arabinofuranosidase from Phanerochaete chrysosporium

摘要

A bifunctional xylosidase/arabinofuranosidase gene (PcXyl) was cloned from the cDNA library of Phanerochaete chrysosporium and further expressed in Pichia pastoris. Enzymatic assay indicated that P. pastoris produced rPcXyl at a level of 26,141 U1~(-1) The xylosidase and arabinofuranosidase activities of rPcXyl were maximized, respectively, at pHs of 5.0 and 5.5 and temperatures of 45°C and 50°C. SDS-PAGE revealed a single band of purified rPcXyl of 83 kDa. Cu~(2+) and Zn~(2+) completely inhibited the enzyme activity of rPcXyl. The enzyme activity of rPcXyl was increased 151%, 126% and 123%, respectively, in the presence of glucose, xylose and arabinose at concentrations of 5 mM. rPcXyl hydrolyzed xylobiose to xylose and xylotriose to xylose and xylobiose, indicating rPcXyl acts as an exo-type enzyme. Additionally, rPcXyl enhanced xylose release from xylan substrates in synergy with rPcXynC