Author/Authors :
Bart Christiaens، نويسنده , , Berlinda Vanloo، نويسنده , , Catherine Gouyette، نويسنده , , Inge Van Vynckt، نويسنده , , Hans Caster، نويسنده , , Josee Taveirne، نويسنده , , Annick Verhee، نويسنده , , Christine Labeur، نويسنده , , Frank Peelman، نويسنده , , Joël Vandekerckhove and Christophe Ampe، نويسنده , , Jan Tavernier، نويسنده , , Maryvonne Rosseneu، نويسنده ,
Latin Abstract :
In this study, we investigated how the nature of the phospholipid head group and the macromolecular structure of the phospholipid, either as a monomer or incorporated into a lipid matrix, influence the activity of lecithin cholesterol acyltransferase (LCAT). As substrates we used 1,2-bis-(1-pyrenebutanoyl)-phosphatidylcholine, 1,2-bis-(1-pyrenebutanoyl)-phosphatidylethanolamine and 1,2-bis-(1-pyrenebutanoyl)-phosphatidyl-alcohols, either as monomers or incorporated into small unilamellar vesicles consisting of dipalmitoylphosphatidylcholine ether. The rate of hydrolysis of the pyrene-labeled phospholipids was determined both by fluorescence and by high performance liquid chromatography. Vmax and Km were calculated for the different substrates. The data show that Vmax is 10- to 30-fold higher for the hydrolysis of monomeric phosphatidylcholine (PC) compared to phosphatidylethanolamine (PE) and the phosphatidylalcohols, while Km values are comparable. When the fluorescent substrates were incorporated into dipalmitoylphosphatidylcholine ether vesicles, we observed a 4- to 10-fold increase of Vmax for PE and the phosphatidylalcohols, and no significant change for Km. Vmax for PC remained the same. Natural LCAT mutants causing Fish-Eye Disease (FED) and analogues of these mutants expressed in Cos-1 cells, had similar activity on monomeric PC and PE. These data suggest that the activity of LCAT is determined both by the molecular structure of the phospholipid and by its macromolecular properties. The LCAT activity on monomeric substrates decreases as: phosphatidylcholine phosphatidylethanolamine phosphatidylpropanol phosphatidylethanol phosphatidylethyleneglycol. The incorporation of PE and the phosphatidylalcohols into a matrix of dipalmitoylphosphatidylcholine decreases the specificity of the phospholipid head group.
NaturalLanguageKeyword :
Lecithin cholesterol acyltransferase , Esterase activity , Substrate , vesicle , phospholipid
