The thermodynamic stability of lipases and proteases from psychrotrophic bacteria

The thermodynamic or conformational stability of psychrotroph lipases and proteases, measured as the Gibbs free energy difference (ΔG) between the native and denatured enzymes, were estimated from enzyme temperature-activity profile data. ΔG estimates of 8–10 kJ/mol and 16–17 kJ/mol were obtained for psychrotroph-derived lipases and proteases, respectively. Pseudomonas fluorescens strain AR-11 protease was unusually thermolabile (ΔG = 3·0–7·6 kJ/mol). These values were compared with values for some mesophilic and thermophilic enzymes and the possible relationship of ΔG to psychrotrophic enzyme heat-resistance is discussed.