Lipase Activity: The Effect of Macromolecules on Structural Transitions and Lipolysis kinetics

Digestive enzyme stability, which depends on its macromolecular environments, is essential for maintaining its function during food processing, storage, and digestion. Conformational transitions of porcine pancreatic lipase (PPL) induced by urea-containing macromolecules including polyethylene glycol, dextran, and Ficoll, followed the unfolding process. The Ficoll 70 system showed two intermediate states of PPL. Lipase in Pluronics maintained a high proportion of the native conformation, illustrating the role of macromolecules in protecting the structure of lipase, in PEG and dextran. Intermediate states of lipase occurred in high concentrations of denaturants. The heterogeneity observed among intermediate states highlights the need for an effective quantitative framework to characterize conformational transitions in macromolecular environments. To further quantify these transitions, analysis of the equilibrium constants (τ) and denaturant binding numbers (m) revealed an antagonistic relationship, reflecting kinetic and thermodynamic differences between the N→I and I→U transitions. The quantitative model employing the equilibrium constant and denaturant binding number describes the conformational transitions of proteins in macromolecular media. Herein, a theoretical framework and experimental approach aid in understanding the regulating effects induced by exposure to food macromolecules and the biophysics of digestive enzymes.