Stability and Conformational Behavior of Lipase in Propanol-Water Solvent Systems

Propanol has emerged as equally important alcohol as methanol and ethanol in lipase-catalyzed systems, but the catalytic and structural behavior of lipases under propanol exposure is poorly described, thereby limiting its potential use. This study investigated the enzymatic properties and conformational dynamics of a mutant lipase from Staphylococcus epidermidis in propanol-water environments. Enzyme stability analysis demonstrated consistent lipolytic activity at varying propanol concentrations. At its optimal temperature of 45°C, the enzyme retained 71-78% relative activity in 10-30% (v/v) propanol and 88-90% in 40% and 50% (v/v) propanol, respectively. The longest half-life of 120 min was achieved at 30% (v/v) propanol and prolonged exposure to 50% (v/v) propanol resulted in a progressive decrease in half-life. Secondary structure analysis revealed the loss of alpha helices by 8-9% and an increase of turn and coil structures in 30 and 50% propanol, reflecting partial and localized alteration rather than complete unfolding. This structural perturbation is supported by molecular dynamics simulations where enhanced backbone flexibility and lid fluctuation were observed. Normal mode analysis further highlights the dynamic architecture of the enzyme with pronounced intrinsic collective motions at three key regions including the lid, N-terminal, and calcium-proximal loop. Together, results suggest structural plasticity is advantageous at low propanol exposure, and the absence of a linear concentration-dependent trend implies a complex dynamic response of this lipase in organic solvents.