《厦大生化》课件.ppt

Chapter26Thebiosynthesisofmembranelipidsandsteroids,Fatssuchasthetriacylglycerolmoleculearewildlyusedtostoreexcessenergyforlateruseandtofulfillotherpurposes.,26.1Phosphatidateisacommonintermediateinthesynthesisofphospholipidsandtriacylglycerols,Glycerolphosphateacyltransferase.,Endoplasmicreticulum/Outermitochondrialmembrane.,Diglycerideacyltransferase.,Triacylglcerolsynthetasecomplexinliver.,26.1.1Thesynthesisofphospholipidsrequiresanactivatedintermediate,Phospholipidsynthesis=thecombinationofadiacylglyceridewithanalcoholAnabolicreactionDiacylglyceroloralcoholshouldbeactivated.,Synthesisfromanactivateddiacylglerol,StructureofCDP-diacylglycerol.,Synthesisformanactivatedalcohol,Inallofbiosyntheses,anactivatedintermediate(UDP-glucose,CDP-diacylglycerol,CDP-alcohol)isformedfromaphosphorylatedsubstrate(glucose-1-phosphate,phosphatide,phosphorylalcohol)andanucleosidetriphosphate.Theactivatedintermediatethenreactswithahydroxylgroup(theterminusofglycogen,thesidechainofserine,oradiacylglycerol).,26.1.2Plasmalogensandotheretherphospholipidsaresynthesizedfromdihydroxyacetonephosphate,Synthesisofanetherphospholipid.,26.1.3Sphingolipidsaresynthesizedfromceramide,鞘氨醇,Synthesisofsphingolipids.,神经酰胺,葡萄糖脑苷脂,神经节苷脂,鞘磷脂,GangliosideGM1.,半乳糖,唾液酸,N-乙酰半乳糖胺,葡萄糖,26.1.4RespiratorydistresssyndromeandTay-Sachsdiseaseresultfromthedisruptionoflipidmetabolism,Tay-Sachsdisease（泰萨氏幼年黑朦白痴症）(1)A1-year-oldinfantwithTay-Sachsdisease.(2)Electronmicrographofaportionofanaffectedbraincell,showingtheabnormalgangliosidedepositsinthelysosomes.,26.2CholesterolissynthesizedfromacetylcoenzymeAinthreestages,Labelingofcholesterol.,26.2.1Thesynthesisofmevalonate,whichisactivatedasisopentenylpyrophosphate,initiatesthesynthesisofcholesterol,Fatesof3-hydroxy-3-methylglutarylCoA.,二羟甲基戊酸,Synthesisofisopentenylpyrophosphate.,Squalenesynthesis.,异戊二烯基转移酶,焦磷酸牻牛儿酯,26.2.2Squalenecyclizestoformcholesterol,Squalenecyclization.,Oxidosqualenecyclase.Cholesterolformation.,26.3Thecomplexregulationofcholesterolbiosynthesistakesplaceatseverallevels,HMG-CoAreductase.,3-hydroxy-3-methylglutarylCoAreductaeThesynthesisofreductasemRNAiscontrolledbysterolregulatoryelementbindingprotein.ThetranslationofreductasemRNA.Thedegradationofthereductase.Phosphorylationdecreasetheactivityoftheredutase.,26.3.1Lipoproteinstransportcholesterolandtriacylglycerolsthroughouttheorganism,ThevesicleinliverthatisreleasingVLDLparticle.,TheLDLparticle(22nm),26.4Importantderivativesofcholesterolincludebilesaltsandsteroidhormones.,Synthesisofbilesalts.,孕烯醇酮,孕酮,睾丸酮,皮质醇,皮质酮,醛固酮,雌二醇,26.4.1Pregnenolone,aprecursorformanyothersteroids,isformedfromcholesterolbycleavageofitssidechain,孕烯醇酮,26.4.2Thesynthesisofprogesteroneandcorticosteroidsfrompregnenolone,Pathwaysfortheformationofprogesterone,cortisol,andaldosterone.,孕酮,26.4.5Thesynthesisofandrogensandestrogensfrompregnenolone,Pathwaysfortheformationforandrogensandestrogens,26.4.6VitaminDisderivedfromcholesterolbythering-splittingactivityoflight,Keyterms,Phosphat