GPI-specific phospholipase D as an apolipoprotein.
Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) has recently been shown to be associated with high-density lipoproteins (HDL) in bovine serum. To determine the distribution of GPI-PLD among lipoproteins and characterize the GPI-PLD-containing lipoproteins in human plasma, we used dextran sulfate and immunoaffinity chromatography to isolate apolipoprotein-specific lipoproteins. This procedure allowed fractionation of lipoprotein particles into those containing apolipoprotein B (Lp B), apolipoproteins AI and AII (Lp AI/AII), or apolipoprotein AI only (Lp AI). In five plasma samples with HDL cholesterol ranging from 40 to 129 mg/dl, 75 +/- 12% (mean +/- SD) of the GPI-PLD activity was associated with Lp AI, 11 +/- 13% with Lp AI/AII, while only 13 +/- 9% was present in plasma devoid of these lipoproteins, suggesting that most of the GPI-PLD in human plasma is associated with apolipoprotein AI. No GPI-PLD activity was detected in Lp B. Further characterization of the GPI-PLD-containing lipoproteins by gel filtration chromatography, nondenaturing poly-acrylamide and agarose gel electrophoresis revealed that GPI-PLD was restricted to an apolipoprotein AI-containing particle or complex that was small (apparent mean Mw of 140 kDa) and distinct from the bulk of HDL. Thus, the majority of plasma GPI-PLD appears to be specifically associated with a small, minor fraction of apolipoprotein AI.
Deeg
M A
MA
Department of Medicine, University of Washington, Seattle 98195.
D000818:Animals; D016632:Apolipoprotein A-I / Q000032:analysis*; D016633:Apolipoprotein A-II / Q000032:analysis*; D001055:Apolipoproteins B / Q000032:analysis*; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D006801:Humans; D008075:Lipoproteins, HDL / Q000097:blood; D010739:Phospholipase D / Q000032:analysis*; D013379:Substrate Specificity
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001055:Apolipoproteins B; D017261:Glycosylphosphatidylinositols; D008075:Lipoproteins, HDL; D010739:Phospholipase D; C065017:glycoprotein phospholipase D