These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Kinetic evidence for phosphatidylethanolamine and triacylglycerol as preferential substrates for hepatic lipase in HDL subfractions: modulation by changes in the particle surface, or in the lipid core.
    Author: Azéma C, Marques-Vidal P, Lespine A, Simard G, Chap H, Perret B.
    Journal: Biochim Biophys Acta; 1990 Aug 28; 1046(1):73-80. PubMed ID: 2397247.
    Abstract:
    Human HDL subfractions, HDL2 (d: 1.085-1.125) and HDL3 (d: 1.125-1.19) labelled with 2-[14C]linoleoylphosphatidylethanolamine and tri-[3H]oleoylglycerol, were incubated with partially purified hepatic triacylglycerol lipase, isolated from human post-heparin plasma. Kinetics of hydrolysis of these two HDL-lipid substrates were followed and were compared to those previously obtained on phosphatidylcholine (G. Simard et al (1989) Biochim. Biophys. Acta 1001, 225-233). (1) The apparent Km obtained for HDL-triacylglycerol was half that for HDL-phosphatidylethanolamine, but the estimated Vmax was higher for the latter. Hence, despite a lower affinity, more molecules of phosphatidylethanolamine than of triacylglycerol were found hydrolysed. A strong correlation was observed between the hepatic lipase activity added and the maximal degradation rates for phosphatidylethanolamine measured in HDL2 and HDL3. (2) A linear relationship was observed in both HDL2 and HDL3 between the respective degradations of the two substrates. The number of phosphatidylethanolamine molecules hydrolysed exceeded that of triacylglycerol by 30% in HDL2 and by 70% in HDL3. HDL2 were 2- and 4-times more reactive than HDL3 for the hydrolysis of phosphatidylethanolamine and triacylglycerol, respectively, taking the Vmax/Km ratio as an indicator of catalytic efficiency. In both HDL subfractions, the calculated Vmax/Km value was 30-50-fold higher for PE and TG than for PC. (3) HDL particles were modified either on their surface by selective enrichment in free cholesterol or in their inner-core by replacement of esterified cholesterol by triacylglycerol in presence of a source of neutral lipid transfer activity. A mild cholesterol enrichment stimulated the phosphatidylethanolamine and triacylglycerol reactivities by 30-60% towards hepatic lipase, whereas increasing the triacylglycerol concentration in HDL was followed by a proportional increase in the amounts of triacylglycerol hydrolysed with no effect on phospholipid degradation.
    [Abstract] [Full Text] [Related] [New Search]