Evaluation of enzyme thermostability by enzyme assay and differential scanning calorimetry A study of alcohol dehydrogenase

Abstract

The thermostability of pure yeast alcohol dehydrogenase has been investigated at various temperatures (50–70 °C) in the presence and absence of sucrose [0, 44.44%(w/w)] by both activity assay and differential scanning calorimetry. The thermal inactivation exhibited non-linear biphasic behavior. The thermal inactivation rate constants and the magnitude of the heat-stable and heat-labile fractions of the enzyme were quantified. The values of the denaturation temperature (T _d ) were experimentally measured by differential scanning calorimetry. A T _d of 63 °C was obtained for the pure alcohol dehydrogenase in the absence of sucrose. Addition of 44.44%(w/w) sucrose yielded a higher denaturation temperature (70 °C). It was found that although activity assay and calorimetry are based on different principles (kinetic in the former case as opposed to thermodynamic in the latter), they yield results that agree well with each other. These results are discussed in the light of both series and parallel enzyme inactivation models.