Inactivation and conformational change of horseradish peroxidase induced by pulsed electric field

Effects of pulsed electric field (PEF) on the structure and activity of horseradish peroxidase (HRP) in buffer solution were studied. The results showed that activity of HRP decreased with the increase in applied electric field strength (5-25 kV/cm) and pulse numbers (207-1242 pulses). 16.7% and 34.7% reduction of HRP relative activity was achieved immediately after PEF treatment at 25 kV/cm for 207 pulses and 22 kV/cm for 1214 pulses, respectively. The temperature of buffer solution did not increase above 40 °C during PEF treatment. The relative activity exhibited a slow reduction after 24 and 48 h of storage at 4 °C. The HRP conformation changed after PEF treatment, as suggested by CD analysis and fluorescence spectroscopy analysis. α-Helix relative content in the HRP decreased by 35.1% and 57.7% after PEF and heating at 100 °C for 5 min, respectively. The intrinsic relative fluorescence intensity (RFI) increased after PEF treatment. The inactivation of PEF-treated HRP was related to the conformational change of α-helix and the increase of RFI.