Thermal denaturation of recombinant human lysozyme from rice: effect of pH and comparison with human milk lysozyme.

Thermal denaturation of recombinant human lysozyme from rice has been studied by differential scanning calorimetry at acidic (4.2), neutral (7.2) and basic (9.2) pH levels at various heating rates, and it has been compared with thermal denaturation of human lysozyme isolated from milk at the same pH levels at a heating rate of 10 °C/min. Data obtained from heat-induced unfolding and subsequent refolding after heating indicate that thermal denaturation of both lysozymes undergoes a two-state process. The maximum temperature of the endothermic peaks and the enthalpy change of denaturation indicate that recombinant and milk lysozymes possess similar thermostability, which is higher at acidic than at neutral pH. On the other hand, both proteins are more thermolabile at basic pH. Lysozyme from human milk shows a higher tendency to aggregate than recombinant human lysozyme from rice during the thermal denaturation process. [ABSTRACT FROM AUTHOR]