Reactivity of HDL subfractions towards lecithin-cholesterol acyltransferase. Modulation by their content in free cholesterol
| Autor: | Gilles Simard, Dominique Loiseau, Bertrand Perret, Andrée Girault |
|---|---|
| Rok vydání: | 1989 |
| Předmět: |
medicine.medical_specialty
Very low-density lipoprotein food.ingredient Biophysics Phospholipid Oleic Acids Biochemistry Lecithin Substrate Specificity Phosphatidylcholine-Sterol O-Acyltransferase chemistry.chemical_compound Endocrinology High-density lipoprotein food Internal medicine medicine Animals Humans Phospholipids Serum Albumin Triglycerides Lipoprotein lipase Cholesterol Reverse cholesterol transport Lipoproteins HDL3 Lipoproteins HDL2 Kinetics Lipoprotein Lipase Milk chemistry Acyltransferase lipids (amino acids peptides and proteins) Cattle Female Cholesterol Esters Lipoproteins HDL Oleic Acid |
| Zdroj: | Biochimica et biophysica acta. 1005(3) |
| ISSN: | 0006-3002 |
| Popis: | (1) Human HDL2 (d 1.070 – 1.125) and HDL3 (d 1.125 – 1.21) labelled with unesterified [14C]cholesterol, were incubated with a source of lecithin-cholesterol acyltransferase. For optimal activity, the reaction required the addition of albumin in excess, at least 3-times greater than the concentration of HDL-free cholesterol. Under such conditions, the reaction appeared saturable. HDL3 was found the most efficient substrate and theVmax values expressed for 1.5 IU LCAT/ml and with an albumin/free cholesterol ratio of 3, were 8.3 nmol free cholesterol esterified/ml per h and 4.1 nmol/ml per h for HDL3 and HDL2, respectively. (2) HDL3 were modified in the presence of VLDL by inducing triacylglycerol lipolysis with a semipurified lipoprotein lipase from bovine milk. The newly formed HDL had gained free cholesterol and phospholipids, so that about 50% of these modified HDL, referred to as light-LIP-HDL3, were reisolated in the HDL2 density range. Light-LIP-HDL3 were enriched mostly in free cholesterol (+160%) and in phospholipid (+40%). Their reactivity towards LCAT was half-reduced compared to parent HDL3, which correlated well with a decrease in their phospholipid/free cholesterol molar ratio. Moreover, HDL3 artificially enriched in free cholesterol and exhibiting a comparable PL/FC behaved like lipolysis-modified HDL in their reactivity towards LCAT. (3) HDL3 were also modified by co-incubation with VLDL (post-VLDL-HDL3), or with VLDL and a source of lipid transfer protein (CET-HDL3). The latter treatment greatly affected the lipid composition of the core particle (−25% esterified cholesterol, +190% TG). In both cases, the moderate decreasing LCAT reactivity observed could be related to the phospholipid/free cholesterol ratio. Thus, like in artificial substrates, the lipid composition of the HDL surface may control the rate of LCAT-mediated cholesterol esterification. |
| Databáze: | OpenAIRE |
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