Location: Healthy Processed Foods ResearchTitle: Effect of pulsed light on activity and structural changes of horseradish peroxidase Author
|Wang, Bei - Jiangsu University|
|Zhang, Yanyan - Chengdu Institute|
|Venkitasamy, Chandrasekar - University Of California|
|Wu, Bengang - Chengdu Institute|
|Ma, Haile - University Of California|
Submitted to: Journal of Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2017
Publication Date: 4/26/2017
Citation: Wang, B., Zhang, Y., Venkitasamy, C., Wu, B., Pan, Z., Ma, H. 2017. Effect of pulsed light on activity and structural changes of horseradish peroxidase. Journal of Food Chemistry. 234:20-25. doi: 10.1016/jfoodchem.2017.04.149.
Interpretive Summary: Peroxidase (POD) is a group of enzymes which widely exist in fruits and vegetables. Presence of POD in foods is not desirable to food processing industries as it causes enzymatic browning of foods during processing, and unpleasant flavor and reduced storability or shelf-life of food products. Therefore, the extent of POD inactivation is a major index in assessing the effectiveness of food processing and quality. Since enzymatic browning could result in a serious negative impact on food quality, preventing or inhibiting enzymatic browning during food processing and storage has become an important goal for high quality foods. Pulsed light (PL) is a FDA-approved, “non-thermal” technology with the potential to be used as an alternative method to inactivate POD. During PL irradiation, high intensity and broad spectrum light is delivered in duration pulses. Photo-thermal and photo-chemical effects generated by the pulses have the potential use for enzyme inactivation. Horseradish peroxidase (HRP) is a typical and widely studied representative enzyme of peroxidase. The biochemical properties and structure of HRP have been well studied. This research investigated the effect of PL on the activity and structural change of HRP. HRP was used as a model enzyme and the influence of PL treatment on the residual enzyme activity and conformation was studied using AFM, fluorescence, and Raman spectroscopic techniques. It was concluded that PL treatment could effectively inactivate HRP by destroying the secondary and tertiary structures of protein in the active center of the enzyme.
Technical Abstract: The objective of this research was to investigate the effects of pulsed light (PL) on the activity and structure of horseradish peroxidase (HRP) in buffer solution. Enzyme residual activities were measured after PL. Surface topography, secondary, and tertiary structures of HRP were determined using atomic force microscopy (AFM), Raman spectroscopy, and fluorescence spectroscopy, respectively. Results showed that a complete inactivation of HRP was achieved by application of 10 pulses of PL at an intensity of 500 J/pulse. The AFM analysis revealed that the aggregation of HRP protein increased and surface roughness decreased with the increase in the PL treatment time. Fluorescence and Raman spectroscopy analysis exhibited that PL treatment destroyed the tertiary and secondary protein structures. The ß-sheet composition was decreased while ß-turn and random coils were increased. PL treatment could effectively inactivate HRP by destroying the secondary and tertiary structures of protein in the active center of the enzyme.