Ultrasonic processing of enzymes: Effect on enzymatic activity of glucose oxidase

The effect of ultrasonication on the enzymatic stability, conformation, and catalytic activity of the important oxidoreductase, glucose oxidase (GOx), was investigated. Thus, buffer-free aqueous solutions of GOx were ultrasonicated (23 kHz at 4 °C) for different periods of time (10, 30, and 60 min) and studied in terms of their enzymatic activity. The ultrasonicated GOx was also studied by UV/vis and circular dichroism (CD) spectroscopy and by thermogravimetric analysis, and compared with pristine GOx. The CD spectra of ultrasonicated GOx showed a different composition with reduced α-helix and β-sheet fractions upon extended sonication compared with the pristine GOx. Along with the changes of the secondary structure, the enzymatic activity measured via HRP-coupled bioassay of the sonicated GOx showed a small corresponding decrease. Low temperature ultrasonic processing of GOx does not appreciably compromise bioactivity.