LCAT in plasma

Lipoproteins are often called pseudomicellar because their outer shell is in part composed of amphipathic phospholipid molecules. Unlike simple micelles, lipoproteins contain apolipoproteins, or apoproteins, in their outer shell and a hydrophobic core of triacylglycerol and cholesteryl esters. Unesterified, or free, cholesterol, which contains a polar group, can be found as a surface component and in the region between the core and surface (Figure 20-1). Most lipoproteins are spherical. However, newly secreted high-density lipoproteins (HDLs) from the liver or intestine are discoidal and require the action of lecithin-cholesterol acyltransferase (LCAT) in plasma to expand their core of neutral lipid and become spherical. The hydrophobic core of the low-density lipoprotein (LDL) molecule may contain two concentric layers one of triacylglycerol and another of cholesteryl ester. 

More than 80% of the cholesteryl esters (CE) found in human plasma derive from the reaction of lecithin cholesterol acyl transferase (LCAT). Since the content of CE in plasma high positively correlates with the incidence of atherosclerosis and myocardial infarction, there has been in the past and still is great interest in investigation of the enzymes involved in lipoprotein metabolism. This overview summarizes some general features, with particular emphasis on investigations carried out in our laboratory (a) the substrates of LCAT in plasma (b), the influence of LCAT on the Upoprotein spectrum (c) the distribution of formed CE after the action of LCAT (d) the impact of cholesteryl ester transfer/exchange protein (CETP) on Upoprotein metabolism. 

---