Synthesis of plasmalogens

Plasmalogensareaclassofglycerophospholipidsthatcontainonevinyl-esterlinkedlongchainalcoholgroupinplaceofoneester-linkedfattyacidchainfoundinotherglycerophospholipids.Aswiththecommonglycerophospholipids,thepolarheadgroupoftheplasmalogensiscomposedofethanolamine,serine,orcholine.Plasmalogensarerelativelyrareinsometissuesbutformasignificantfractionofthemembranesinnervoustissue.Someofthestepsinplasmalogenbiosynthesisarelocalizedinperoxisomes,andsomeperoxisomaldisordersimpairplasmalogenbiosynthesis.Oneofthestartingmaterialsforplasmalogenbiosynthesisisdihydroxyacetonephosphatefromglycolysis,whichisusedtoformtheglycerolbackboneoftheplasmalogen.Inthefirststep,thethree-carbonbackboneisesterifiedwithafattyacid.Thisfattyacidesteristhenexchangedleavinganether-linkedlong-chainalcoholbound.Reductionofthecarbonylonthedihydroxyacetonebackboneleavesahydroxygrouptobeesterifiedwithanotherfattyacidsidechain.Thepolarheadgroupsuchasethanolamineisthenadded,andthealcoholchainmodifiedinthelaststeptoformthevinyl-alcoholsidechainthatcharacterizesplasmalogens.PlasmalogensserveasastartingpointforthereleaseofarachidonicacidbyphospholipaseA2andthesynthesisofsignalingmoleculesderivedfromarachidonicacidsuchasprostaglandins.OneplasmalogencalledPAFactsthroughaG-proteincoupledreceptorasapotentplateletactivatorandclottingagent.Thedoublebondofplasmalogensmakesthemmoresensitivetooxidationthanothermembranelipids,andmayhelptoprotectcellsfromoxidativedamage.AdecreaseintheabundanceofplasmalogenshasbeenobservedinsomeneurologicaldisorderssuchasAlzheimer’sdisease.

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