Hydrolysis of phosphatidylcholine liposomes by lysosomal phospholipase A is maximal at the phase transition temperature of the lipid substrate |
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Authors: | Michel Vandenbranden Georges De Gand Robert Brasseur Fabienne Defrise-Quertain Jean-Marie Ruysschaert |
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Institution: | (1) Laboratoire de Chimie Physique des Macromolécules aux Interfaces, Université Libre de Bruxelles, Boulevard du Triomphe, CP 206/2, 1050 Brussels, Belgium |
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Abstract: | We have measured the rate of hydrolysis of liposomes made of DL- -dipalmitoylphosphatidylcholine (DPPC) and L- -dimyristoylphosphatidylcholine by a soluble fraction of highly purified lysosomes isolated from rat liver. Phospholipids are hydrolyzed into lysophospho-lipids and fatty acids at a rate which is maximal near the temperature characteristic of the gel to liquid crystalline phase transition of the lipid bilayer. This strong influence of the physical properties of the substrate on the enzyme activity suggests a structural analogy between the lysosomal phospholipases of the A type (EC 3.1.1.32 and EC 3.1.1.4) and the pancreatic phospholipase A2. |
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