Effect of Organic Solvents on Porcine Pancreatic Lipase Thermal Aggregation

Proteins tend to form inactive aggregates under harsh conditions used in industrial processes. Lipases are enzymes that hydrolyse triglycerides to glycerol and free fatty acids, but are able to catalyse various other transformations in the presence of organic solvents.

The main objective of this study was to investigate lipases behavior at high temperature and in presence of organic solvents.

Heat-induced aggregation of porcine pancreatic lipase (PPL) was followed by UV-visible spectroscopy at 400 nm wavelength for 600 seconds, at the isoelectric point (pH 5, phosphate solution) and 50°C, and in presence or absence of various percentages of dimethyl sulfoxide (DMSO), propanol, isopropanol, acetone and trifluoroethanol (TFE). Possible positioning of each organic solvent molecule relative to PPL was investigated using docking method.

Native enzyme aggregated under aforementioned conditions and amorphous aggregates formed which were visible to the naked eye. From the tested solvents, DMSO reduced protein aggregation in a concentration-dependent manner. On the other hand, protein aggregation intensified by adding any of propanol, isopropanol, acetone or TFE. This effect was more pronounced in TFE and propanol compared to isopropanol and acetone.

Solvents with lower polarity led to aggregation, while solvent with higher polarity inhibited PPL aggregation, and DMSO could be effectively used to counteract lipase aggregation.