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

The thermostable esterase from the bacteriumUreibacillus thermosphaericuswas expressed with Trx tag from plasmid pET32b-estUT1 under T7 promoter inE. coliBL21(DE3). The specific activity and relative thermal stability of the tagged enzyme increased from 45.2 to 65.8% (1 h at 70 degrees C). 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 (k(cat)/K-M) 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.