INHIBITION OF PANCREATIC LIPASE BY OVALBUMIN AND BETA-LACTOGLOBULIN-A AT THE AIR-WATER-INTERFACE

The kinetics of ovalbumin and β-lactoglobulin A adsorption at the air/water interface were studied in the abence or presence of 1,2-didecanoylglycerol (dicaprin) monolayer. The lipolytic inhibition capacities of ovalbumin and β-lactoglobulin A are explained in terms of their adsorption kinetic properties. The adsorption of the proteins can be controlled by a diffusion and/or an adsorption energy barrier step. Assuming the adsorption to be diffusion-controlled, the apparent diffusion coefficient (Dapp was calculated and compared with the diffusion coefficient (D) measured independently. When calculated, Dapp was found to be lower than D, which shows that an adsorption energy barrier exists. The energy barrier of β-lactoglobulin A was found to be lower than tat of ovalbumin. Assuming the adsorption energy barrier to be a rate-controlled process, the adsorption constant was calculated. β-Lactoglobulin A has a higher adsorption rate. The surface rheological dilatational properties during adsorption of the proteins and enzymes were also studied. In the presence of β-lactoglobulin A, the previously elastic properties of the lipid monolayer became viscoelastic. A mixed monolayer of ovalbumin/dicaprin or β-lactoglobulin A/dicaprin was spread and used to study the inhibition of horse pancreatic lipase activity at the air/water interface. A critical lipid/protein ratio was found to exist, above which enzymatic hydrolysis of dicaprin was observed. This molar ratio is 1 in the case of a mixed ovalbumin/dicaprin monolayer and 9 in the case of a mixed β-lactoglobulin A/dicaprin monolayer. © 1990.