Effect of the single mutation N9Y on the catalytical properties of xylanase Xyn11A from Cellulomonas uda: a biochemical and molecular dynamic simulation analysis.

Cellulomonas uda produces Xyn11A, moderately thermostable xylanase, with optimal activity at 50 °C and pH 6.5. An improvement in the biochemical properties of Xyn11A was achieved by site-directed mutagenesis approach. Wild-type xylanase, Xyn11A-WT, and its mutant Xyn11A-N9Y were expressed in Escherichia coli, and then both enzymes were purified and characterized. Xyn11A-N9Y displayed optimal activity at 60 °C and pH 7.5, an upward shift of 10 °C in the optimum temperature and an upward shift of 1 unit in optimum pH; also, it manifested an 11-fold increase in thermal stability at 60 °C, compared to that displayed by Xyn11A-WT. Molecular dynamics simulations of Xyn11A-WT and Xyn11A-N9Y suggest that the substitution N9Y leads to an array of secondary structure changes at the N-terminal end and an increase in the number of hydrogen bonds in Xyn11A-N9Y. Based on the significant improvements, Xyn11A-N9Y may be considered as a candidate for several biotechnological applications.