Author: Herr Dr. Amoneit
Last saved by: Saritas, Sevim (Euro Fed Lipid)
Company: Microsoft

Gastric Lipase Interacting with Lipid Membrane Model: Atomic Force Microscopy Visualization
Véronique Vié^1, Gilles Paboeuf^1, Sophie Chever^2, Fanny Guyomarch^2, Stéphane Pezennec^2, Saïd Bouhallab^2, Frédéric Carrière^3, Claire Bourlieu^2
^1Institut de Physique, Université de Rennes1, Rennes, France 
^2Science et Technologie du Lait et de l’Oeuf, INRA Rennes, France
^3 Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, INSERM, Marseille, France

In the context of the neonatal digestion of milk fat globule, we studied the interaction between a gastric lipase and lipid membrane models in order to identify key parameters in the first step of enzyme anchoring to the membrane before the onset of the catalytic activity. Indeed, little is known about the effect of the lipid nature constituting the external membrane of the milk fat globule on the digestion process.
Lipid Langmuir films were used to mimic the outer leaflet of the external membrane of the milk fat globule. Different lipid mixtures with variable physical phases, surface charge and lateral packing had allowed identifying the nature of the enzyme/membrane interactions. Recombinant dog gastric lipase (rDGL) was used as model of the human gastric lipase.
A combination of different techniques including tensiometry, ellipsometry, atomic force microscopy gave an insight on the ability to the enzyme to access and insert in the lipid membrane. Indeed, tensiometry is related to the ability of the molecule to insert in the lipid film, ellipsometry gives information on the amount of enzyme interacting with the membrane (with or without penetration) while atomic force microscopy allows visualization at the nanoscale the lateral organization of the enzyme embedded in the membrane. In addition, natural lipid mixtures (with and without enzyme substrate) extracted from cow buttermilk were used to complete the set of membrane lipids.
Our funding shows that a large amount of rDGL molecules is located close to the lipid membrane and exclusively in the LE lipid phase while little insertion is noticed. Moreover, the molecular interactions are clearly impacted by the nature of the lipid membrane.