Crystal structure of an acetylesterase from Talaromyces cellulolyticus and the importance of a disulfide bond near the active site.

Carbohydrate esterase catalyzes the de-O or de-N-acylation of substituted saccharides in plant cell walls and thus has great potential for industrial biomass saccharification. We recently identified the putative carbohydrate esterase family 3 (CE3) from Talaromyces cellulolyticus. Here, we prepared the recombinant catalytic domain of the enzyme and crystallized it. The crystal structure was determined to 1.5 Å resolution. From the structural analysis, it was elucidated that a n-octyl-β-D-glucopyranoside bound to near the catalytic triad (Ser10, Asp179 and His182) and was buried in the active site cavity. Site-directed mutagenesis showed that the N-terminal disulfide bond located near the catalytic triad is involved in the activity and structural stability of the enzyme.