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1、二、其他脂类的生物合成Biosynthesisofphosphatidicacid.Afattyacylgroupisactivatedbyformationofthefattyacyl–CoA,thentransferredtoesterlinkagewithL-glycerol3-phosphate,formedineitherofthetwowaysshown.PhosphatidicacidisshownherewiththecorrectstereochemistryatC-2oftheglycerolmolecule.Toconservespaceinsubsequentfig
2、ures,bothfattyacylgroupsofglycerophospholipids,andallthreeacylgroupsoftriacylglycerols,areshownprojectingtotheright.Phosphatidicacidinlipidbiosynthesis.Phosphatidicacidistheprecursorofbothtriacylglycerolsandglycerophospholipids.Themechanismsforhead-groupattachmentinphospholipidsynthesisaredescribe
3、dlaterinthissection.1.三酰甘油的合成Someofthefattyacidsreleasedintothebloodareusedforenergy(inmuscle,forexample),andsomearetakenupbytheliverandusedintriacylglycerolsynthesis.Thetriacylglycerolformedintheliveristransportedinthebloodbacktoadiposetissue,wherethefattyacidisreleasedbyextracellularlipoproteinl
4、ipase,takenupbyadipocytes,andreesterifiedThetriacylglycerolcycle.Inmammals,triacylglycerolmoleculesarebrokendownandresynthesizedinatriacylglycerolcycleduringstarvation.Someofthefattyacidsreleasedbylipolysisoftriacylglycerolinadiposetissuepassintothebloodstream,andtheremainderareusedforresynthesiso
5、ftriacylglycerol.Insulinstimulatesconversionofdietarycarbohydratesandproteinstofat.Individualswithdiabetesmellituslackinsulin;inuncontrolleddisease,thisresultsindiminishedfattyacidsynthesis,andtheacetyl-CoAarisingfromcatabolismofcarbohydratesandproteinsisshuntedinsteadtoketonebodyproduction.People
6、insevereketosissmellofacetone,sotheconditionissometimesmistakenfordrunkenness.RegulationoftriacylglycerolsynthesisbyinsulinGlyceroneogenesis.Thepathwayisessentiallyanabbreviatedversionofgluconeogenesis,frompyruvatetodihydroxyacetonephosphate(DHAP),followedbyconversionofDHAPtoglycerol3-phosphate,wh
7、ichisusedforthesynthesisoftriacylglycerol.Regulationofglyceroneogenesis.(a)Glucocorticoidhormonesstimulateglyceroneogenesisandgluconeogenesisintheliver,whilesuppressingglyceroneogenesisintheadiposetissue(byrecipr
