Phylogenetic functional and structural characterization of a GH10xylanase active at extreme conditions of temperature and alkalinity

摘要

Endoxylanases active under extreme conditions oftemperature and alkalinity can replace the use of highly pollutant chemicals inthe pulp and paper industry. Searching for enzymes with these properties, wecarried out a comprehensive bioinformatics study of the GH10 family. Thephylogenetic analysis allowed the construction of a radial cladogram in whichprotein sequences putatively ascribed as thermophilic and alkaliphilic appearedgrouped in a well-defined region of the cladogram, designated TAK Cluster. Oneamong five TAK sequences selected for experimental analysis (Xyn11) showedextraordinary xylanolytic activity under simultaneous conditions of hightemperature (90 °C) and alkalinity (pH 10.5). Addition of a carbohydrate bindingdomain (CBM2) at the C-terminus of the protein sequence further improved theactivity of the enzyme at high pH. Xyn11 structure, which has been solved at1.8 Å resolution by X-ray crystallography, reveals an unusually high number ofhydrophobic, ionic and hydrogen bond atomic interactions that could account forthe enzyme’s extremophilic nature.