References: Lecithin
Biochim Biophys Acta. 1989 Feb 20;1001(3):325-37.
Conversion of apolipoprotein-specific high-density lipoprotein populations during incubation of human plasma.
Nichols AV, Blanche PJ, Shore VG, Gong EL.
Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
Incubation studies were performed on plasma obtained from subjects selected for relatively low levels of high-density lipoprotein cholesterol (HDL-C) (no greater than 30 mg/dl) and particle size distributions enriched in the HDL3 subclass. Incubation (12 h, 37 degrees C) of plasma in the presence or absence of lecithin: cholesterol acyltransferase activity produces marked alteration in size profiles of both major apolipoprotein-specific HDL3 populations (HDL3(AI w AII), HDL3 species containing both apolipoprotein A-I and apolipoprotein A-II, and HDL3(AI w/o AII), HDL3 species containing apolipoprotein A-I) as isolated by immunoaffinity chromatography. In the presence or absence of lecithin: cholesterol acyltransferase activity, plasma incubation results in a shift of HDL3(AI w AII) species (initial mean sizes of major components, approx. 8.8 and 8.0 nm) predominantly to larger particles (mean size, 9.8 nm). A less prominent shift to smaller particles (mean size, 7.8 nm) accompanies the conversion to larger particles only when the enzyme is active. Combined shifts to larger (mean size, 9.8 nm) and smaller (mean size, 7.4 nm) particles are observed for HDL3(AI w/o AII) particles (mean size, 8.3 nm) also only in the presence of enzyme activity. However, in the absence of enzyme activity, HDL3(AI w/o AII) species, unlike the HDL3(AI w AII) species, are converted to smaller (mean size 7.4 nm) rather than to larger particles. Like native HDL2b(AI w/o AII) particles, the larger HDL3(AI w/o AII) conversion products exhibit a protein moiety with molecular weight equivalent to four apolipoprotein A-I molecules per particle; small HDL3(AI w/o AII) products are comprised predominantly of particles with two apolipoprotein A-I per particle. Inc
J Lipid Res. 1995 May;36(5):967-74.
In vitro expression of natural mutants of human lecithin:cholesterol acyltransferase.
Qu SJ, Fan HZ, Blanco-Vaca F, Pownall HJ.
Department of Medicine, Baylor College of Medicine, Houston, TX, USA.
Fish-eye disease (FED) and familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) are rare disorders of lipid metabolism linked to mutations in the LCAT gene. Eleven LCAT cDNA constructs associated with FED and FLD were prepared by site-directed mutagenesis and expressed in COS-6 cells. Analysis of total RNA from wild-type, FED, and FLD transfectants revealed that all contained LCAT-specific mRNA. Western blot analysis demonstrated that all LCAT transfectants synthesized LCAT. Mean LCAT secretion by FED transfectants was slightly lower than secretion by wild-type transfectants, whereas secretion by FLD transfectants was much lower. The specific activities of FED and FLD LCAT against model high density lipoproteins were 6% and 11%, respectively, of wild-type activity. The ratios of the LCAT activities against low density lipoproteins to those against model high density lipoproteins decreased in the order FED mutants > FLD mutants approximately wild type. FED and FLD LCAT mutants are different: the former are more active against low density lipoproteins, and the latter are less secretion-competent. The greater reactivity of FED LCAT against low density lipoproteins may explain the relative mildness of the clinical manifestations of FED compared to those of FLD.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7658168&dopt=Abstract lecithin
J Biol Chem. 1993 Feb 15;268(5):3114-9.
High density lipoprotein interconversions in rat and man as assessed with a novel nontransferable apolipopeptide.
Ponsin G, Pulcini T, Sparrow JT, Gotto AM Jr, Pownall HJ.
Laboratoire de Metabolisme des Lipides, Hopital de L'Antiquaille, Lyon, France.
A nontransferable peptide analog of a plasma apolipoprotein diacyl lipid-associating peptide (diLAP) incorporates into model reassembled high density lipoproteins (R-HDL). In whole plasma in vitro, diLAP irreversibly transfers to native rat HDL2 and human HDL3, but not to rat HDL1 or human HDL2. The rate of transfer is dependent on the physical state of the lipid in the R-HDL. Exogenous cholesterol promotes the formation of larger HDL. When diLAP-labeled R-HDL were injected into rats, the diLAP that initially associated with HDL2 transferred to HDL1 over a period of 48 h. The rate of clearance of diLAP-labeled HDL was slower than that of apoA-I. The liver was the preferred site for diLAP-labeled HDL1 uptake. In contrast, diLAP-labeled HDL2 were associated with liver, ovaries, and adrenal glands, with the adrenal grands exhibiting the highest specific association. DiLAP was not found in the kidneys. These data show that 1) rat HDL is cleared more slowly than rat apoA-I; 2) HDL is removed from the plasma compartment as a particle; 3) there are tissue-specific differences in the removal of rat HDL1 and HDL2; 4) HDL2 is a precursor to HDL1; and 5) cholesterol and the activity of lecithin:cholesterol acyltransferase are essential to HDL remodeling.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8428990&dopt=Abstract lecithin
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