Crystal structure of an acetyl esterase complexed with acetate ion provides insights into the catalytic mechanism

We previously reported the crystal structure of an acetyl esterase (TcAE206) belonging to carbohydrate esterase family 3 from Talaromyces cellulolyticus. In this study, we solved the crystal structure of an S10A mutant of TcAE206 complexed with an acetate ion. The acetate ion was stabilized by three hydrogen bonds in the oxyanion hole instead of a water molecule as in the structure of wild-type TcAE206. Furthermore, the catalytic triad residue His182 moved 0.8 Å toward the acetate ion upon substrate entering the active site, suggesting that this movement is necessary for completion of the catalytic reaction.
Highlights • The crystal structure of TcAE206_S10A with acetate ion was solved at 1.4 Å resolution. • The complex structure revealed the catalytic mechanism. • His182, which moves 0.8 Å toward the acetate ion, is necessary for enzymatic activity. • This study provides insights into the substrate specificity of fungal CE3 enzymes.