Degradation of High-Density Lipoproteins (HDL) In Vitro

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Abstract
An isolation procedure is described in which, in the presence of a SH-blocking agent, DTNB, LP-B, and albumin-free HDL2 and HDL3 were isolated. Subfractionation on hydroxylapatite column chromatography of HDL2 and HDL3 respectively, gave three parent fractions of characteristic polypeptide composition. HDL3 fractions I and II contained the thin immunoprecipitin line peptide, LP-D. Incubation in vitro of HDL3 fraction II caused degradation of the fraction, simultaneously with the appearance of newly formed cholesterol ester and a consumption of lecithin. Re-chromatography of the degraded HDL3 fraction II gave three daughter fractions, one of which contained LP-D with lysolecithin as its characteristic phosphatide and some neutral lipids (cholesterol). It is suggested that the degradation was caused by lecithin: cholesterol acyltransferase reaction and that LP-D may be the specific carrier for the substrate lecithin and/or the product lysolecithin of HLD3.