Thermostable Esterase estUT1 from Ureibacillus thermosphaericus: Effect of TrxA Tag on the Enzyme Properties

Abstract

The thermostable esterase from the bacterium Ureibacillus thermosphaericus was expressed with Trx tag from plasmid pET32b-estUT1 under T7 promoter in E. coli BL21(DE3). The specific activity and relative thermal stability of the tagged enzyme increased from 45.2 to 65.8% (1 h at 70°С). The additional TrxA tag does not affect the pH optimum of enzyme activity and substrate specificity. At the same time, the absence of the TrxA tag resulted in a significant increase in the stability of estUT1 in during incubation with various chemicals, including ethanol and methanol. The maximum catalytic efficiency (kcat/KM) for esterase was observed in the absence of the TrxA tag and was 280.0 s−1 mM−1. Thereby fusion with TrxA tag promotes the enzyme secretion in the dissolved form, but reduces its thermal stability.