Membrane lipid composition differentially modulates the function of human plasma platelet activating
1Department of Biotechnology, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar, Punjab 160062, India. apande@niper.ac.in
Biochimica Et Biophysica Acta
|September 28, 2010
Summary
Human plasma platelet activating factor-acetylhydrolase (HpPAF-AH) activity increases upon membrane binding. Membrane composition, altered by cholesterol, influences HpPAF-AH binding, penetration, and function.
Area of Science:
- Biochemistry
- Enzymology
- Lipid Metabolism
Background:
- Human plasma platelet activating factor-acetylhydrolase (HpPAF-AH) is a calcium-independent phospholipase A₂ superfamily enzyme.
- HpPAF-AH hydrolyzes phospholipids at the sn-2 position and acts on substrates like oxidized phospholipids.
- The enzyme circulates on lipoprotein particles, interacting with lipids.
Purpose of the Study:
- To investigate how membrane vesicle lipid composition affects purified HpPAF-AH function.
- To determine the impact of varying cholesterol content in POPC and DPPC vesicles on enzyme binding, penetration, and activity.
Main Methods:
- Purified HpPAF-AH was studied using phospholipid vesicles with varied cholesterol content.
- Physicochemical properties of vesicles were assessed using fluorescent probes.
- Enzyme membrane binding, partial membrane penetration, and activity were quantified.
Main Results:
- Membrane binding was found to increase HpPAF-AH activity (interfacial activation).
- Varying vesicle lipid composition, specifically cholesterol levels, modulated enzyme binding and penetration.
- Changes in physicochemical properties of vesicles differentially affected HpPAF-AH activity based on lipid composition.
Conclusions:
- HpPAF-AH exhibits interfacial activation upon binding to membrane surfaces.
- The lipid milieu of membrane vesicles significantly influences HpPAF-AH's interaction and functional activity.
- Understanding these lipid-enzyme interactions is crucial for comprehending HpPAF-AH's role in biological systems.
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