Cyberlipid
Search Cyberlipid

Ethanolamine glycerophospholipids

Analogous structures to those described for choline phospholipids exist for the ethanolamine phospholipids. The pattern of fatty acid distribution generally shows a higher degree of unsaturation than that found in choline phospholipids.
The diacyl derivative (1,2-diacyl-sn-glycero-3-phosphorylethanolamine, phosphatidylethanolamine) was originally named "cephalin". This phospholipid is a zwitterion over the pH range of 2-7 and is in the anionic form in the range 7-10.

pict79.gif

In mammalian and plant tissues this component usually occurs in lesser amounts than phosphatidylcholine. In bacteria, it is the principal phospholipid present.
Several experiments have provided data related with a role of phosphatidylethanolamine in the formation of diacylglycerol as second messenger. It appears that this mechanism plays a role in the transformation and differentiation of cells (McNulty S et al., Neurosci Lett 1991, 139, 183; Lang D et al., J Neurochem 1995, 65, 810; Momchilova A et al., Int J Biochem cell Biol 1999, 31, 311). The importance of that messenger production in cell signaling remains to be reinvestigated.
The formation and the multiple functions of phosphatidylethanolamine in mammalian cells have been reviewed (Vance JE et al., Biochim Biophys Acta 2013, 1831, 543).

Activated platelets and monocytes were shown to generate phosphatidylethanolamine with 15-HETE or 12-HETE acylated at the sn-2 position of glycerol (Maskrey BH et al., J Biol Chem 2007, 282, 20151). It was determined that the formation of these phosphatidylethanolamine species in immune cells could contribute to lipoxygenase signaling in inflammation. Monocytes and macrophages generate phosphatidylethanolamine with a keto acid, 15-ketoeicosatetraenoic acid, which is a bioactive mediator activating peroxysome proliferator-activated receptor (Hammond VJ et al., J Biol Chem 2012, 287, 41651). Besides phosphatidylserine, five phosphatidylethanolamine species are externaluzed during the activation of platelets by thrombin or collagen (Clark SR et al., PNAS 2013, 110, 5875).

Phosphono derivatives : After the discovery of 2-aminoethylphosphonic acid in lipid extracts of the sea anemone (Kittredge JS et al., Biochemistry 1962, 1, 624), unusual phosphatidylethanolamine analogues containing a carbon-phosphorus bond instead of the classical carbon-oxygen-phosphorus bond have been described in marine invertebrates and protozoa (Tetrahymena pyriformis). They were first reported in 1966 in Tetrahymena as glycerophosphonolipids (Liang CR et al., Biochim Biophys Acta 1966, 125, 548) but, later, they were identified in that species as derivative of chimyl alcohol (Thomson GA, Biochemistry 1967, 6, 2015) : an alcohol is linked with an ether bond in sn-1 of the glycerol molecule. They were also identified in fish, some mammals, egg yolk, insects, several invertebrates and even in some plants (Mukhamedova KS et al., Chem Nat Compounds 2000, 36, 329). Thus, egg yolk contains about 1% of phosphonolipids, mainly all as phosphatidylethanolamine.
These phosphonolipids, often termed phosphonylethanolamine, are extremely resistant to acid or enzymatic hydrolysis. They were proposed as a possible artificial pulmonary surfactant.

The alk-1′-enyl, acyl derivative (ethanolamine plasmalogen) occurs widely in nature, mainly present in high concentration in the white matter (myelin) of the nervous system, in the heart and the kidney. It is practically absent in fungi, plants and bacteria (except in obligate anaerobes).

pict80.gif

The fatty acid acylated at the 2-position of glycerol is most frequently polyunsaturated (arachidonic or docosahexaenoic acid). Ethanolamine plasmalogens constitute more than 80 mol% of the ethanolamine phospholipid pool in non-neuronal brain membranes and more than 60 mol% in neurons and synaptosomes (Han X et al., J Neurochem 2001, 77, 1168). Those found in white matter contain p