Abstract
A novel, family GH10 enzyme, Xyn10B from Acidothermus cellulolyticus 11B was cloned and expressed in Escherichia coli. This enzyme was purified to homogeneity by binding to regenerated amorphous cellulose. It had higher binding on Avicel as compared to insoluble xylan due to the presence of cellulose-binding domains, CBM3 and CBM2. This enzyme was optimally active at 70 degrees C and pH 6.0. It was stable up to 70 degrees C while the CD spectroscopy analysis showed thermal unfolding at 80A degrees C. Xyn10B was found to be a trifunctional enzyme having endo-xylanase, arabinofuranosidase and acetyl xylan esterase activities. Its activities against beechwood xylan, p-Nitrophenyl arabinofuranoside and p-Nitrophenyl acetate were found to be 126,480, 10,350 and 17,250 U mu mol(-1), respectively. Xyn10B was highly active producing xylobiose and xylose as the major end products, as well as debranching the substrates by removing arabinose and acetyl side chains. Due to its specific characteristics, this enzyme seems to be of importance for industrial applications such as pretreatment of poultry cereals, bio-bleaching of wood pulp and degradation of plant biomass.