Thermophilic esterase APE1547 from Aeropyrum pernix K1 contained a β-propeller with seven blades. There are three hydrogen bonding interactions(Thr127-Gly154,Leu182- Arg145-Glu122) between blades 3 and 4 in the β-propeller domain of the APE1547. To examine the role of these hydrogen bonds, we eliminated these three hydrogen bonds between blades 3 and 4, by site-directed mutagenesis. The analysis results of kinetics, thermostability and differential scanning calorimetry(DSC) of the mutants show that Kcat/Km value of each mutation increased, and stability decreased dramatically than wild-type protein. These results strongly suggest that the three specific hydrogen bonds played an important role on maintaining the stability and activity of the esterase APE1547.
