Human plasma platelet-activating factor acetylhydrolase. Oxidatively fragmented phospholipids as substrates

Area of Science:

• Biochemistry
• Lipid Metabolism
• Enzymology

Background:

• Platelet-activating factor (PAF) acetylhydrolase is a human plasma enzyme.
• It is associated with low-density lipoprotein (LDL) particles.
• This enzyme specifically degrades oxidatively damaged phospholipids.

Purpose of the Study:

• To identify potential substrates for PAF acetylhydrolase.
• To investigate the enzyme's specificity towards phospholipids with varying sn-2 residues.
• To determine if oxidation fragments of phospholipids are substrates.

Main Methods:

• Synthesis of phosphatidylcholines with varying sn-2 residue lengths.
• Enzymatic assays using PAF acetylhydrolase and synthesized phospholipids.
• Oxidation of phospholipids followed by phospholipase C treatment and GC/MS analysis.
• Analysis of hydrolysis products using gas chromatography/mass spectroscopy.

Main Results:

• Hydrolysis efficiency decreased with increasing sn-2 residue length.
• An omega-oxo function in the sn-2 residue significantly affected hydrolysis.
• Oxidized phospholipids yielded fragmented sn-2 residues.
• The enzyme specifically degraded these oxidatively fragmented phospholipids.

Conclusions:

• Oxidation fragments the sn-2 residue of phospholipids.
• PAF acetylhydrolase specifically targets and degrades these oxidatively fragmented phospholipids.
• This enzyme plays a role in the metabolism of oxidized lipids.