The effect of ultrasound on the properties and conformation of glucoamylase

In this study, the effects of ultrasonic treatment on the enzyme activity of glucoamylase were investigated and the mechanism of the effect was explored by determining their conformational changes. The enzyme activity was increased by 21.07% over the control with ultrasound at 420 W for 10 min at 60 °C, and Vmax and Km values of glucoamylase were also increased. After ultrasonic treatment at 420 W, thermodynamic experiments of glucoamylase showed that Ea, ΔG, ΔH decreased but slight increase in ΔS was observed. In addition, after the treatment, the UV spectra showed that the number of tryptophan and tyrosine on glucoamylase surface increased, and the contents of α-helix and random coil increased by 17.8%, 12.41%, respectively, through the circular dichroism spectrum scanning. Besides, fluorescence spectra indicated that the absorption of tryptophan has a red shift. Furthermore, fourier transform infrared spectra suggested that the glucoamylase was significantly influenced by ultrasound. The results indicated that the activity of glucoamylase could be modified by ultrasonic treatment mainly in terms of the variation of their conformation.