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Ether lipid

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(Redirected fromGlycerol ether)
Structure of an etherphospholipid.Note ether at first and second positions.
Plasmalogen.Note ether at first position, and ester at second position.
Platelet-activating factor.Note ether at first position, andacylgroup at second position.

Inbiochemistry,anether lipidrefers to anylipidin which the lipid "tail" group is attached to theglycerolbackbone via anether bondat any position. In contrast, conventionalglycerophospholipidsandtriglyceridesare triesters.[1]Structural types include:

  • Ether phospholipids:phospholipids are known to have ether-linked "tails" instead of the usual ester linkage.[1]
    • Ether on sn-1, ester on sn-2:"ether lipids" in the context of bacteria and eukaryotes refer to this class of lipids. Compared to the usual1,2-diacyl-sn-glycerol(DAG), the sn-1 linkage is replaced with an ester bond.[1][2][3]

Based on whether the sn-1 lipid is unsaturated next to the ether linkage, they can be further divided intoalkenyl-acylphospholipids( "plasmenylphospholipid", 1-0-alk-1’-enyl-2-acyl-sn-glycerol) andalkyl-acylphospholipids( "plasmanylphospholipid" ). This class of lipids have important roles in human cell signaling and structure.[4]

    • Ether on sn-2 and sn-3:this class with flippedchiralityon the phosphate connection is called an "archaeal ether lipid". With few (if any) exceptions, it is only found amongarchaea.The part excluding the phoshphate group is known asarchaeol.[5][6]
  • Ether analogues of triglycerides:1-alkyldiacyl-sn-glycerols (alkyldiacylglycerols) are found in significant proportions in marine animals.[5]
  • Other ether lipids:a number of other lipids not belonging to any of the classes above contain the ether linkage. For example,seminolipid,a vital part of the testes and sperm cells, has a ether linkage.[1]

The term "plasmalogen"can refer to any ether lipid with avinyl etherlinkage, i.e. ones with a carbon-carbondouble bondnext to the ether linkage. Without specification it generally refers to alkenyl-acylphospholipids, but "neutral plasmalogens" (alkenyldiacylglycerols) and "diplasmalogens" (dialkenylphospholipids) also exist.[1]The prototypical plasmalogen isplatelet-activating factor.[7]

In eukaryotes

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Biosynthesis

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The formation of the ether bond in mammals requires two enzymes,dihydroxyacetonephosphate acyltransferase(DHAPAT) andalkyldihydroxyacetonephosphate synthase(ADAPS), that reside in theperoxisome.[8]Accordingly, peroxisomal defects often lead to impairment of ether-lipid production.

Monoalkylglycerol ethers (MAGEs) are also generated from 2-acetyl MAGEs (precursors of PAF) byKIAA1363.

Functions

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Structural

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Plasmalogens as well as some 1-O-alkyl lipids are ubiquitous and sometimes major parts of thecell membranesinmammals.[9]Theglycosylphosphatidylinositolanchor of mammalian proteins generally consist of an 1-O-alkyl lipid.[1]

Second messenger

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Differences between thecatabolismof ether glycerophospholipids by specificphospholipasesenzymesmight be involved in the generation of lipidsecond messenger systemssuch asprostaglandinsandarachidonic acidthat are important in signal transduction.[10]Ether lipids can also act directly in cell signaling, as theplatelet-activating factoris an ether lipid signaling molecule that is involved inleukocytefunction in the mammalianimmune system.[11]

Antioxidant

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Another possible function of the plasmalogen ether lipids is asantioxidants,as protective effects againstoxidative stresshave been demonstrated incell cultureand these lipids might therefore play a role in serumlipoproteinmetabolism.[12]This antioxidant activity comes from the enol ether double bond being targeted by a variety ofreactive oxygen species.[13]

Synthetic ether lipid analogs

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Synthetic ether lipid analogs havecytostatic and cytotoxicproperties, probably by disrupting membrane structure and acting asinhibitorsof enzymes within signal transmission pathways, such asprotein kinase Candphospholipase C.

A toxic ether lipid analoguemiltefosinehas recently been introduced as an oral treatment for the tropical diseaseleishmaniasis,which is caused byleishmania,aprotozoalparasite with a particularly high ether lipid content in its membranes.[14]

In archaea

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The cell membrane ofarchaeaconsist mostly of ether phospholipids. These lipids have a flipped chirality compared to bacterial and eukaryotic membranes, a conundrum known as the "lipid divide".The" tail "groups are also not simply n-alkyl groups, but highly methylated chains made up of saturatedisoprenoidunits (e.g.phytanyl).[15]

Among different groups of archaea, diverse modifications on the basicarchaeolbackbone have emerged.

  • The two tails can be linked together, forming a macrocyclic lipid.[15]
  • Bipolar macrocyclic tetraether lipids (caldarchaeol), with two glycerol units connected by two C40"tail" chains, formcovalentlylinked 'bilayers'.[16][15]
    • Some such covelant bilayers feature crosslinks between the two chains, giving an H-shaped molecule.[15]
    • Crenarchaeolis a tetraether backbone with cyclopentane and cyclohexane rings on the cross-linked "tail" s.[15]
  • Some lipids replace the glycerol backbone with four-carbon polyols (tetriols).[15]

In bacteria

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Ether phospholipids are major parts of the cell membrane in anaerobic bacteria.[1]These lipids can be variously 1-O-alkyl, 2-O-alkyl, or 1,2-O-dialkyl. Some groups have, like archaea, evolved tetraether lipids.[17]

In prokaryotes

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Some ether lipids found in marine animals are S-batyl alcohol,S-chimyl alcohol,and S-selachyl alcohol.

See also

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References

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  1. ^abcdefgChristie W."Ether lipids - glyceryl ethers, plasmalogens, aldehydes, structure, biochemistry, composition and analysis".lipidmaps.org.
  2. ^Dean JM, Lodhi IJ (February 2018)."Structural and functional roles of ether lipids".Protein & Cell.9(2): 196–206.doi:10.1007/s13238-017-0423-5.PMC5818364.PMID28523433.
  3. ^Ford DA, Gross RW (July 1990)."Differential metabolism of diradyl glycerol molecular subclasses and molecular species by rabbit brain diglyceride kinase".The Journal of Biological Chemistry.265(21): 12280–6.doi:10.1016/S0021-9258(19)38342-5.PMID2165056.S2CID1042240.
  4. ^Dean, JM; Lodhi, IJ (February 2018)."Structural and functional roles of ether lipids".Protein & Cell.9(2): 196–206.doi:10.1007/s13238-017-0423-5.PMC5818364.PMID28523433.
  5. ^abVillanueva, Laura; von Meijenfeldt, F. A. Bastiaan; Westbye, Alexander B.; Yadav, Subhash; Hopmans, Ellen C.; Dutilh, Bas E.; Damsté, Jaap S. Sinninghe (January 2021)."Bridging the membrane lipid divide: bacteria of the FCB group superphylum have the potential to synthesize archaeal ether lipids".The ISME Journal.15(1): 168–182.Bibcode:2021ISMEJ..15..168V.doi:10.1038/s41396-020-00772-2.PMC7852524.PMID32929208.
  6. ^"Di- and Tetra-Alkyl Ether Lipids of the Archaea".lipidmaps.org.
  7. ^Watson RR, De Meester F, eds. (2014).Omega 3 fatty acids in brain and neurological health.Elsevier Academic Press.doi:10.1016/C2012-0-06006-1.ISBN978-0-12-410527-0.
  8. ^Hajra AK (1995). "Glycerolipid biosynthesis in peroxisomes (microbodies)".Progress in Lipid Research.34(4): 343–64.doi:10.1016/0163-7827(95)00013-5.PMID8685243.
  9. ^Paltauf F (December 1994). "Ether lipids in biomembranes".Chemistry and Physics of Lipids.74(2): 101–39.doi:10.1016/0009-3084(94)90054-X.PMID7859340.
  10. ^Spector AA, Yorek MA (September 1985)."Membrane lipid composition and cellular function".Journal of Lipid Research.26(9): 1015–35.doi:10.1016/S0022-2275(20)34276-0.PMID3906008.Archived fromthe originalon 2008-10-10.Retrieved2007-03-08.
  11. ^Demopoulos CA, Pinckard RN, Hanahan DJ (October 1979)."Platelet-activating factor. Evidence for 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine as the active component (a new class of lipid chemical mediators)".The Journal of Biological Chemistry.254(19): 9355–8.doi:10.1016/S0021-9258(19)83523-8.PMID489536.
  12. ^Brosche T, Platt D (August 1998). "The biological significance of plasmalogens in defense against oxidative damage".Experimental Gerontology.33(5): 363–9.doi:10.1016/S0531-5565(98)00014-X.PMID9762517.S2CID20977817.
  13. ^Engelmann B (February 2004). "Plasmalogens: targets for oxidants and major lipophilic antioxidants".Biochemical Society Transactions.32(Pt 1): 147–50.doi:10.1042/BST0320147.PMID14748736.
  14. ^Lux H, Heise N, Klenner T, Hart D, Opperdoes FR (November 2000). "Ether--lipid (alkyl-phospholipid) metabolism and the mechanism of action of ether--lipid analogues in Leishmania".Molecular and Biochemical Parasitology.111(1): 1–14.doi:10.1016/S0166-6851(00)00278-4.PMID11087912.
  15. ^abcdefCaforio, Antonella; Driessen, Arnold J.M. (2017)."Archaeal phospholipids: Structural properties and biosynthesis"(PDF).Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids.1862(11): 1325–1339.doi:10.1016/j.bbalip.2016.12.006.PMID28007654.S2CID27154462.
  16. ^Koga Y, Morii H (November 2005)."Recent advances in structural research on ether lipids from archaea including comparative and physiological aspects".Bioscience, Biotechnology, and Biochemistry.69(11): 2019–34.doi:10.1271/bbb.69.2019.PMID16306681.
  17. ^Grossi, V; Mollex, D; Vinçon-Laugier, A; Hakil, F; Pacton, M; Cravo-Laureau, C (1 May 2015)."Mono- and dialkyl glycerol ether lipids in anaerobic bacteria: biosynthetic insights from the mesophilic sulfate reducer Desulfatibacillum alkenivorans PF2803T".Applied and Environmental Microbiology.81(9): 3157–68.Bibcode:2015ApEnM..81.3157G.doi:10.1128/AEM.03794-14.PMC4393425.PMID25724965.
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