Catalytic behavior of pancreatic lipase in crowded medium for hydrolysis of medium-chain and long-chain lipid: An isothermal titration calorimetry study

Pancreatic lipase is an interfacial enzyme. The kinetic parameters of pancreatic lipase derived from heat release in crowded surroundings have not been reported. In this work, the effect of crowded medium on the catalytic activity of porcine pancreatic lipase (PPL) during lipid digestion was investigated by Isothermal Titration Calorimetry (ITC). The results showed that dietary polysaccharide Ficoll400 tended to increase the catalytic efficiency of PPL for both glyceryl trioleate and glyceryl trioctanoate substrates, whereas Dextran20 decreased the activity of the enzyme. The change in the fluorescence intensity and secondary structural content of PPL parallels the change of k cat / K m , of PPL, which was further confirmed in PEG2000. The findings of this research improve understanding of macromolecular crowding effects on interfacial catalysis by lipases. Moreover, it provides a useful method for research on enzyme kinetics in crowed medium by ITC .