【精选】生物化学简明教程第四版第九章糖代谢二.ppt

葡萄糖→→→丙酮酸→乙酰CoA→→→CO2+H2O丙酮酸的氧化Regulationofthepyruvatedehydrogenasecomplex.ThecomplexisinhibitedbyitsimmediateproductsNADHandacetylCoA.Thepyruvatedehydrogenasecomponentisalsoregulatedbycovalentmodification.Aspecifickinasephosphorylatesandinactivatespyruvatedehydrogenaseandaphosphataseactivesthedehydrogenasebyremovingthephosphoryl.Thekinaseandthephosphatasealsoarehighlyregulatedenzymes.WhydoesTPPdeficiencyleadprimarilytoneurologicaldisorders?Thenervoussystemreliesessentiallyonglucoseasitsonlyfuel.Incontrastmostothertissuescanusefatsasasourceoffuelforthecitricacidcycle.Theproductofaerobicglycolysispyruvatecanenterthecitricacidcycleonlythroughthepyruvatedehydrogenasecomplex.Arsenitepoisoning.Arseniteinhibitsthepyruvatedehydrogenasecomplexbyinactivatingthedihydrolipoamidecomponentofthetransacetylase.Somesulfhydrylreagentssuchas23-dimercaptoethanolrelievetheinhibitionbyformingacomplexwiththearsenitethatcanbeexcreted.三羧酸循环(tricarboxylicacidcycleTCA)三羧酸循环包含8个步骤：（1）乙酰辅酶A与草酰乙酸缩合形成柠檬酸(2)柠檬酸脱水生成顺乌头酸然后加水生成异柠檬酸草酰琥珀酸(4)α-酮戊二酸氧化脱羧生成琥珀酰辅酶A琥珀酸脱氢酶延胡索酸（8）苹果酸氧化生成草酰乙酸CH3CO-SCoA+3NAD++FAD+GDP+H3PO4+2H2Overviewofthecitricacidcycle.Thecitricacidcycleoxidizestwo-carbonunitsproducingtwomoleculesofCO2onemoleculeofGTPandhighenergyelectronsintheformofNADHandFADH2.Thelinkbetweenglycolysisandthecitricacidcycle.PyruvateproducedbyglycolysisisconvertedintoacetylCoAthefuelofthecitricacidcycle.1mol葡萄糖在有氧分解时所产生的ATP的mol数糖有氧分解中的能量变化三羧酸循环的生物学意义TCA循环是糖、脂肪和蛋白质转化的枢纽三羧酸循环的代谢调节乙醛酸途径(glyoxylatepathway)Theglyoxylatepathway.Theglyoxylatecycleallowsplantsandsomemicroorganismstogrowonacetatebecausethecyclebypassesthedecarboxylationstepsofthecitricacidcycle.Theenzymesthatpermittheconversionofacetateintosuccinate—isocitratelyaseandmalatesynthase—areboxedinblue