Investigation of the Mechanisms of Pulsed Electric Fields on Inactivation of Enzyme: Lysozyme

Abstract

Lysozyme was selected as a model enzyme to investigate the effects of pulsed electric fields (PEF) on its activity and structure. The irreversible inactivation of lysozyme in sodium phosphate buffer (10 mM, pH 6.2) induced by PEF at 35 kV/cm followed a first-order model when the treatment time was longer than 300 micros. Unfolding of lysozyme structure was induced by PEF, accompanied by the cleavage of disulfide bonds and self-association aggregation when the applied PEF dosage was higher than a critical level. The inactivation of lysozyme by PEF was correlated to the loss of alpha-helix in secondary structure. The relative residual activity of PEF-treated lysozyme was in close agreement with the relative molar ellipticity at 208 nm. Both PEF- and heat-induced inactivations of lysozyme were correlated to the alteration of the secondary structure of lysozyme, but the effects of PEF and heat treatment on secondary structure were inconsistent.

Quantitative and real time detection of pulsed electric field induced damage on Escherichia coli cells and sublethally injured microbial cells using flow cytometry in combination with fluorescent techniques

“…Following PEF treatments from 15 to 35 kV/cm, there was a steady decrease in the percentage of cF-positive subpopulation from 98% to 8%, indicating the intracellular enzymes were inactivated under stress of PEF. This may be supported by the recent studies on the impacts of PEF on enzymes and proteins (Toschi, Lugli, Biscarini, & Zerbetto, 2009;Zhao & Yang, 2010;Zhao, Yang, Lu, Tang, & Zhang, 2007).…”

Impact of critical high‐intensity pulsed electric field processing parameters on oxidative enzymes and color of broccoli juice

“…Zhao and Yang () observed a correlation between the loss of secondary and tertiary structures of lysozyme and their inactivation by HIPEF. In the same way, a loss of α‐helix in secondary structure was observed when papain and lysozyme were subjected to HIPEF treatment (Yeom, Zhang, & Dunne, ; Zhao, Yang, Lu, Tang, & Zhang, ). Likely, HIPEF polarize the protein molecule and change its conformation, resulting in the protein inactivation (Perez & Pilosof, ), which could explain the LOX and PPO inactivation observed when broccoli juice was treated by HIPEF.…”

Microbial and enzymatic stability of fruit juice-milk beverages treated by high intensity pulsed electric fields or heat during refrigerated storage

“…It is known that HIPEF and thermal enzyme inactivation mechanisms are related to the unfolding of proteins due to changes in their secondary structure (Zhao, Yang, Lu, Tang & Zhang, 2007). However, there is no available information about whether these changes are persistent during an extended storage period, so it should not de dismissed the fact that a posterior folding of the enzyme structure could occur, leading to an increase on its activity.…”