Distribution and localization of lecithin:cholesterol acyltransferase and cholesteryl ester transfer activity in A-I-containing lipoproteins.
Two types of A-I-containing lipoproteins are found in human high density lipoproteins (HDL): particles with A-II (Lp(A-I with A-II] and particles without A-II (Lp(A-I without A-II]. We have studied the distribution of lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer (CET) activities in these particles. Lp(A-I with A-II) and Lp(A-I without A-II) particles were isolated from ten normolipidemic subjects by anti-A-I and anti-A-II immunosorbents. Most plasma LCAT mass (70 +/- 15%), LCAT (69 +/- 16%), and CET (81 +/- 15%) activities were detected in Lp(A-I without A-II). Some LCAT (mass: 16 +/- 7%, activity: 17 +/- 8%) and CET activities (7 +/- 8%) were detected in Lp(A-I with A-II). To determine the size subspecies that contain LCAT and CET activities, isolated Lp(A-I with A-II) and Lp(A-I without A-II) particles of six subjects were further fractionated by gel filtration column chromatography. In Lp(A-I without A-II), most LCAT and CET activities were associated with different size particles, with the majority of the LCAT and CET activities located in particles with hydrated Stokes diameters of 11.6 +/- 0.4 nm and 10.0 +/- 0.6 nm, respectively. In Lp(A-I with A-II), most of the LCAT and CET activities were located in particles similar in size: 11.1 +/- 0.4 nm and 10.6 +/- 0.3 nm, respectively. Ultracentrifugation of A-I-containing lipoproteins resulted in dissociation of both LCAT and CET activities from the particles. Furthermore, essentially all CET and LCAT activities were recovered in the non-B-containing plasma obtained by anti-LDL immunoaffinity chromatography. This report, therefore, provides direct evidence for the association of LCAT and CET protein with A-I-containing lipoproteins. Our conclusions pertain to fasting normolipidemic subjects and may not be applicable to hyperlipidemic or nonfasting subjects.
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A / Q000097:blood* / Q000302:isolation & purification; D002352:Carrier Proteins / Q000097:blood*; D053480:Cholesterol Ester Transfer Proteins; D002788:Cholesterol Esters / Q000097:blood*; D002846:Chromatography, Affinity; D005260:Female; D006023:Glycoproteins; D006801:Humans; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood*; D008297:Male; D008970:Molecular Weight; D002785:Sterol O-Acyltransferase / Q000097:blood*
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A; C506642:CETP protein, human; D002352:Carrier Proteins; D053480:Cholesterol Ester Transfer Proteins; D002788:Cholesterol Esters; D006023:Glycoproteins; D008075:Lipoproteins, HDL; D002785:Sterol O-Acyltransferase