Effect of pulsed light on activity and structural changes of horseradish peroxidase

- Pulsed light could rapidly and completely inactivate horseradish peroxidase.
- Pulsed light led to protein aggregation and denaturation.
- Pulsed light could unfold the tertiary structure of protein molecules.
- Pulsed light caused the secondary structure change of horseradish peroxidase.

The objective of this research was to investigate the effects of pulsed light on the activity and structure of horseradish peroxidase in buffer solution. Enzyme residual activities were measured. Surface topography, secondary, and tertiary structures of horseradish peroxidase were determined using atomic force microscopy (AFM), Raman spectroscopy, and fluorescence spectroscopy, respectively. Results showed that a complete inactivation of horseradish peroxidase was achieved by application of 10 pulses of pulsed light treatment at an intensity of 500 J/pulse. The AFM analysis revealed that the aggregation of enzyme protein increased and surface roughness decreased with the increase in the treatment time. Fluorescence and Raman spectroscopy analysis exhibited that pulsed light destroyed the tertiary and secondary protein structures. The β-sheet composition was decreased while β-turn and random coils were increased. Pulsed light could effectively inactivate horseradish peroxidase by destroying the secondary and tertiary structures of protein in the active center of the enzyme.