Inactivation and structural change of horseradish peroxidase treated with supercritical carbon dioxide

The influence of supercritical carbon dioxide (SCCO2) at 55 °C on inactivation of horseradish peroxidase (HRP) in buffer solution, pH 5.6, was studied while its structural change was analyzed by far UV-circular dichroism (CD) and tryptophan fluorescence spectroscopy. SCCO2 treatment had significant effects on the residual activity of HRP, the least residual activity was only 12% at 30 MPa. HRP’s secondary and tertiary structures were changed. The α-helix relative content in the secondary structure decreased and the intrinsic relative fluorescence intensity (RFI) increased as the pressure of SCCO2 treatment was elevated. The HRP’s inactivation closely corresponded to the loss of α-helix relative content and the increase of RFI. After a 7-day storage at 4 °C, the restoration of residual activity and the reversion of the α-helix relative content were observed while RFI resumed with exception of the 30 MPa treatment.