Kinetic study of the thermal denaturation of a hyperthermostable extracellular α-amylase from Pyrococcus furiosus

Hyperthermophilic enzymes are of industrial importance and interest, especially due to their denaturation kinetics at commercial sterilisation temperatures inside safety indicating time–temperature integrators (TTIs). The thermal stability and irreversible thermal inactivation of native extracellular Pyrococcus furiosus α-amylase were investigated using differential scanning calorimetry, circular dichroism and Fourier transform infrared spectroscopy. Denaturation of the amylase was irreversible above a Tm of approximately 106 °C and could be described by a one-step irreversible model. The activation energy at 121 °C was found to be 316 kJ/mol. Using CD and FT-IR spectroscopy it was shown that folding and stability greatly increase with temperature. Under an isothermal holding temperature of 121 °C, the structure of the PFA changes during denaturation from an α-helical structure, through a β-sheet structure to an aggregated protein. Such data reinforces the use of P. furiosus α-amylase as a labile species in TTIs.