Interaction of lipoprotein lipase with homogeneous lipid emulsions

C E MacPhee, R Y S Chan, W H Sawyer, W F Stafford, G J Howlett, Cait MacPhee

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Abstract

The central function of lipoprotein lipase (LpL) is to hydrolyze triacylglycerols in chylomicrons and very low density lipoproteins. We have examined the binding of purified milk lipoprotein lipase to homogeneous synthetic lipid emulsions. Emulsions composed of either naturally occurring ester-linked lipids or the non-hydrolyzable ether analogues were prepared by sonication and pressure extrusion, and fractionated by sucrose density gradient centrifugation. Flotation analysis using the analytical ultracentrifuge indicated that the individual fractions were relatively homogeneous with respect to size with flotation coefficients and molecular weights for the separated fractions ranging from 100 to 1100 S and 5.2 x 10(7) to 6.0 x 10(8), respectively. Purified milk lipoprotein lipase bound with high affinity and in a saturable manner to emulsions prepared from the non-hydrolyzable ether-linked lipid analogues of 1-oleoyl, 2-palmitoyl phosphatidylcholine and triolein. At low concentrations of LpL, the enzyme caused aggregation of the emulsion particles by interparticle cross-linking. At higher LpL concentrations, the flotation coefficient of the emulsions decreased significantly with a concomitant increase in particle density. At saturation, the number of LpL monomers bound to lipid particles of radii 67, 75, and 79 nm was 1315, 1449, and 1466, respectively. The results demonstrate close packing of LpL on the lipid surface and are consistent with there being little disruption to the overall structure of the emulsion particle.

Original languageEnglish
Pages (from-to)1649-1659
Number of pages11
JournalJournal of lipid research
Volume38
Issue number8
Publication statusPublished - Aug 1997

Keywords

  • ether-linked lipids
  • sedimentation velocity
  • sedimentation equilibrium
  • protein-lipid interactions
  • flotation velocity
  • lipid monolayer
  • LOW-DENSITY LIPOPROTEINS
  • HEPATIC TRIACYLGLYCEROL LIPASE
  • RECEPTOR-RELATED PROTEIN
  • POST-HEPARIN PLASMA
  • APOLIPOPROTEIN-C-II
  • UNESTERIFIED CHOLESTEROL
  • RICH LIPOPROTEINS
  • BOUNDARY ANALYSIS
  • TERMINAL DOMAIN
  • VESICLES

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