Enzyme-containing liposomes can endogenously produce membrane-constituting lipids

Area of Science:

• Biochemistry
• Lipid Metabolism
• Synthetic Biology

Background:

• Giant vesicles (liposomes) allow real-time monitoring of biochemical reactions.
• Previous studies showed vesicle degradation via injected phospholipase A2.
• This study investigates the possibility of synthesizing lipids within a giant vesicle.

Purpose of the Study:

• To determine if lipid membrane precursors can be synthesized in situ within giant vesicles.
• To explore the application of the first step of the salvage pathway for 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC) synthesis.
• To lay the groundwork for constructing complete metabolic pathways within liposomes.

Main Methods:

• Preparation of giant vesicles from 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC) and palmitoyl-CoA.
• Microinjection of sn-glycerol-3-phosphate-acyltransferase into the vesicles.
• Observation of in situ lipid synthesis and subsequent vesicle morphology changes using light microscopy.

Main Results:

• In situ production of the lipid precursor 1-palmitoyl-sn-glycerol-3-phosphate was successfully catalyzed by the microinjected enzyme.
• The synthesized lipid precursor was incorporated into the vesicle membrane.
• Vesicle shrinkage and formation of smaller liposomes on the inner surface were observed due to altered membrane chemistry.

Conclusions:

• Demonstrated the feasibility of localized lipid synthesis within giant vesicles using a key step of the POPC salvage pathway.
• This finding supports the potential for creating self-sufficient liposomes capable of synthesizing their own components.
• Future research may focus on combining multiple enzymes to achieve complete metabolic pathways within liposomes.