Investigation of the mechanisms of pulsed electric fields on inactivation of enzyme: lysozyme.

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.