Comparative study of inactivation and conformational change of lysozyme induced by pulsed electric fields and heat

A comparative study of inactivation and conformational change of lysozyme induced by pulsed electric fields (PEF) at 35 kV/cm and heat at 100C was carried out. The results showed that both PEF- and heat-induced inactivation of lysozyme followed a first-order model. While the relative residual activity (RRA) values of lysozyme induced by PEF and heat were similar, the conformational changes in tertiary and secondary structures were different in the two treatments demonstrated by 8-aniline-1-naphthalene sulfonate-binding and intrinsic fluorescence and circular dichroism analysis, indicating the different enzyme inactivation mechanisms. The tertiary and secondary structures of lysozyme unfolded coincidentally with the decrease of lysozyme RRA values from 92 to 62% induced by PEF, suggesting that lysozyme treated with PEF did not form a molten globule. However, in heat treatment, lysozyme with RRA values from 90 to 78% had the same backbone secondary structure as the native protein, but with significant changes in tertiary structure.