title: Hydrolysis of phosphatidylcholine by hepatic lipase in discoidal and spheroidal recombinant high-density lipoprotein.
abstract: Hepatic lipase (HL) hydrolysis of phosphatidylcholine (PC) was studied in recombinant high-density lipoprotein particles (r-HDL). r-HDL were made from cholate mixed micelles that contained PC, apo AI, and, in some cases, unesterified cholesterol. r-HDL were characterized using chemical composition, nondenaturing gradient gel electrophoresis, transmission electron microscopy, and dynamic light scattering. The r-HDL were found to be discoidal and in the size range of native HDL. Upon treatment of cholesterol-containing r-HDL with lecithin-cholesterol acyltransferase (LCAT), to form cholesteryl ester, the discoidal r-HDL became spheroidal. The effects of r-HDL morphology and size on HL activity were studied on r-HDL made of palmitoyloleoyl-PC, unesterified cholesterol, cholesteryl ester, and apolipoprotein AI. Spheroidal r-HDL were hydrolyzed at a faster rate than discoidal r-HDL. Protein-poor r-HDL were hydrolyzed by HL at a faster rate than protein rich r-HDL. Unesterified cholesterol had no apparent effect on particle PC hydrolysis. The hydrolysis of different species of PC [dipalmitoyl (DPPC), dioleoyl(DOPC), palmitoylarachidonoyl (PAPC), and palmitoyloleoyl (POPC)] in r-HDL was also investigated. In discoidal r-HDL, we found that POPC >/= DOPC = PAPC/DPPC. However, in LCAT-treated spheroidal r-HDL, POPC = DOPC > PAPC/DPPC. In both discoidal and spheroidal rHDL, DPPC containing r-HDL were not hydrolyzed to a significant extent. Collectively, these studies demonstrate that the physico-chemical properties of particles (such as phospholipid packing and phospholipid acyl composition) play a significant role in hydrolysis of HDL phospholipid by HL and, therefore, in reverse cholesterol transport.
authors.affiliation: Department of Biochemistry, Bowman Gray School of Medicine, Winston-Salem, North Carolina 27157-1016, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Tansey
authors.forename: T Y
authors.initials: TY
authors.lastname: Thuren
authors.forename: W G
authors.initials: WG
authors.lastname: Jerome
authors.forename: R R
authors.initials: RR
authors.lastname: Hantgan
authors.forename: K
authors.initials: K
authors.lastname: Grant
authors.forename: M
authors.initials: M
authors.lastname: Waite
mesh_terms: D016632:Apolipoprotein A-I / Q000378:metabolism; D002788:Cholesterol Esters / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D007834:Lasers; D008049:Lipase / Q000378:metabolism*; D008075:Lipoproteins, HDL / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008099:Liver / Q000201:enzymology*; D008854:Microscopy, Electron; D010316:Particle Size; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D012542:Scattering, Radiation; D013379:Substrate Specificity
chemical_list: D016632:Apolipoprotein A-I; D002788:Cholesterol Esters; D008075:Lipoproteins, HDL; D010713:Phosphatidylcholines; D011994:Recombinant Proteins; D007862:Phosphatidylcholine-Sterol O-Acyltransferase; D008049:Lipase