Ether lipid

Ether lipids are lipids in which one or more of the carbon atoms on glycerol is bonded to an alkyl chain via an ether linkage, as opposed to the usual ester linkage.

Ether lipids are called plasmalogens (1-O-1'-alkenyl-2-acylglycerophospholipids) if these are glycerol-containing phospholipids with an unsaturated O-(1-alkenyl) (vinyl ether) group at the first position on the glycerol chain.

Platelet-activating factor (PAF) is an ether lipid which has an acetyl group instead of an acyl chain at the second position (SN-2).

The formation of the ether bond in mammals requires two enzymes, dihydroxyacetonephosphate acyltransferase (DHAPAT) and alkyldihydroxyacetonephosphate synthase (ADAPS), that reside in the peroxisome. Accordingly, peroxisomal defects often lead to impairment of ether-lipid production.

Monoalkylglycerol ethers (MAGEs) are also generated from 2-acetyl MAGEs (precursors of PAF) by KIAA1363.

Plasmalogens as well as some 1-O-alkyl lipids are ubiquitous and sometimes major parts of the cell membranes in mammals and anaerobic bacteria. In archaea, ether lipids are the major polar lipids in the cell envelope and their abundance is one of the major characteristics that separate this group of prokaryotes from the bacteria. In these cells, diphytanylglycerolipids or bipolar macrocyclic tetraethers can form covalently linked 'bilayers'.

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