The neutral lipid composition and size of recombinant high density lipoproteins regulates lecithin:cholesterol acyltransferase activity

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Abstract
Recombinant high density lipoprotein (rHDL) particles were prepared from purified lipids and human apoproteins, and the ability of these complexes to act as substrates for purified lecithin:cholesterol acyltransferase (LCAT) was determined. Increasing the triacylglycerol content relative to cholesteryl ester in rHDL markedly decreased the maximum catalytic potential of LCAT. Kinetic analysis showed that the Vmax of the LCAT reaction was significantly and negatively correlated to the triacylglycerol content. The apparent Km was not directly affected by relative neutral lipid content, but was significantly related to protein and surface lipid content as well as to particle size. These results suggest that while particulate size may regulate the interaction between LCAT and HDL, the relative neutral lipid content of the particle may play a major role in regulating the catalytic potential of the enzyme, particularly with HDL from hypertriglyceridemic patients.Key words: high density lipoproteins, lecithin:cholesterol acyltransferase, model lipoproteins, triacylglycerol, cholesteryl ester.