Ether lipids are a traditional family of lipids with ether-linked structures that are chemically differ from their more prevalent acyl relatives. Ether lipids can be of two types, alkyl-acylphospholipids, or alkenyl-acylphospholipids (plasmalogens), characterized by an ether bond of an alkyl or alkenyl chain with the OH group in position one of the glycerol-phosphate. Usually, these lipids contain ethanolamine or choline as head group. In mammals, ether lipids constitute about 20% of the total phospholipid mass, but the tissue distribution varies. The highest levels are found in the brain, heart, spleen, and white blood cells, while liver has scant amount of intracellular ether lipids.
Structure of ether lipids
Common phospholipids are composed of the three-carbon alcohol glycerol to which fatty acyl molecules are coupled via an ester bond to the first and second carbon of the glycerol molecule (designated the R1 and R2 positions, respectively). Ether lipids have a similar structure to the phospholipids. The difference is that it has an alkyl chain attached to the R1 position via an ether bond. The alcohol moiety attached to the phosphate group in ether lipids is usually choline or ethanolamine, but it may also be inositol or serine. In mammals, most of the ether lipids are plasmalogens, which contain a vinyl ether-linked fatty alcohol at position R1.
Figure 1. Chemical structures of common phospholipids and two classes of ether lipids.
Functions of ether lipids
Ether lipids are a unique class of phospholipids that can contribute unique structural features to biological membranes, thereby influencing factors such as membrane fluidity and membrane fusion. In addition, ether lipids are involved in a variety of biological functions. The main functions of ether lipids are shown below.
Ether lipids are a major structural component of cell membranes. The incorporation of ether-linked alkyl chains in phospholipids alters their physical properties and affects membrane dynamics. This is largely attributed to the lack of a carbonyl oxygen at the R1 position, which facilitates stronger intermolecular hydrogen bonding between the headgroups. Moreover, the vinyl-ether linkage of plasmalogens at the R1 position allows the proximal regions of the R1 and R2 chains to become parallel, favoring close alignment, therefore permitting tighter packing of phospholipids in the membrane resulting in decreased membrane fluidity and increased rigidity.
Model membranes enriched in plasmalogens have a high tendency to form an inverse hexagonal phase (non-lamellar inverse hexagonal structures) at lower temperatures. Since a transition from a lamellar (no curvature) to an inverted hexagonal (negative curvature) phase is required for membrane fusion, this property of plasmalogens allows them to facilitate the membrane trafficking process.
Plasmalogens serve as a store of polyunsaturated fatty acids that can be released by specific stimulant molecules, especially in membranes that are stimulated electro physiologically, and they may act as intracellular signaling compounds. Thus, at least two plasmalogen-selective enzymes of the phospholipase A2 type are involved in the degradation of plasmalogens, releasing arachidonic and docosahexaenoic acids from position R2 for eicosanoid or docosanoid production, respectively, as part of signaling mechanisms.
Studies on ether lipids have shown that ether lipids are also involved in a variety of biological functions, including regulating cell differentiation, and reducing oxidative stress through their ability to act as potential endogenous antioxidants.
What we offer
Alfa Chemistry supplies a wide range of ether lipid products for companies researching vaccines. If you cannot find the product you need, please contact us. We also offer product customization according to customer's detailed requirements.
Our products and services are for research use only and cannot be used for any clinical purposes.