Studies on the alkali-tolerance mechanism of the xylanase by site-directed or random mutagenesis

摘要

Using site-directed mutagenesis, we were able to confirm that the substitutions of Asn-71 of the xylanase led to the decrease in specific activity of the xylanase, especially in an alkaline pH range. Though other sites of residue could also influence the pH optimum of the xylanase, they did not affect their activity in the alkaline pH range as much as that of Asn-71. In addition, all mutant xylanases studied in this paper changed their pH optima to a more acidic value. So, the Asn-71 of XYN from B. pumilus A-30 plays a critical role in the alkali-tolerance of the family G/11 xylanases. More kinetic data are needed in order to reveal the alkali-tolerant mechanism of the alkaline xylanase of family G/11.