生物化学简明教程糖代谢二学习PPT教案.pptx

丙酮酸的氧化Regulationofthepyruvatedehydrogenasecomplex.
Thecomplexisinhibitedbyitsimmediateproducts,NADHandacetylCoA.Thepyruvatedehydrogenasecomponentisalsoregulatedbycovalentmodification.Aspecifickinasephosphorylatesandinactivatespyruvatedehydrogenase,andaphosphataseactivesthedehydrogenasebyremovingthephosphoryl.Thekinaseandthephosphatasealsoarehighlyregulatedenzymes.WhydoesTPPdeficiencyleadprimarilytoneurologicaldisorders?Thenervoussystemreliesessentiallyonglucoseasitsonlyfuel.Incontrast,mostothertissuescanusefatsasasourceoffuelforthecitricacidcycle.Theproductofaerobicglycolysis,pyruvate,canenterthecitricacidcycleonlythroughthepyruvatedehydrogenasecomplex.Arsenitepoisoning.Arseniteinhibitsthepyruvatedehydrogenasecomplexbyinactivatingthedihydrolipoamidecomponentofthetransacetylase.Somesulfhydrylreagents,suchas2,3-dimercaptoethanol,relievetheinhibitionbyformingacomplexwiththearsenitethatcanbeexcreted.三羧酸循环(tricarboxylicacidcycle,TCA)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CH3CO-SCoA+3NAD++FAD+GDP+H3PO4+2H2Overviewofthecitricacidcycle.Thecitricacidcycleoxidizestwo-carbonunits,producingtwomolecules
ofCO2,onemoleculeofGTP,andhighenergyelectronsintheformofNADHandFADH2.Thelinkbetweenglycolysisandthecitricacidcycle.
PyruvateproducedbyglycolysisisconvertedintoacetylCoA,thefuelofthecitricacidcycle.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.Theglyoxylatecycleallowsplantsandsome
microorganismstogrowonacetatebecausethecyclebypassesthedecarboxylationstepsofthecitricacidcycle.Theenzymesthatpermittheconversionofacetateintosuccinate—isocitratelyaseandmalatesynthase—areboxedinblue.2乙酰CoA+NAD++2H2O乙醛酸途径的意义乙醛酸循环途径加入碘乙酸或氟化物糖无氧分解和有氧分解是体内糖分解的主要途径，但不是唯一途径。磷酸戊糖途径的反应过程三、单糖分子间基团转换6(葡萄糖-6-磷酸)+12NADP++6H2O磷酸戊糖途径的调节1、生成NADPH，为细胞的各种合成反应提供还原力。
NADPH是体内重要的供氢体，参与多种生物合成反应。如合成脂肪酸、胆固醇及类固醇激素都需要大量的NADPH。
2、为DNA、RNA和多种辅酶的合成提供核糖-5-磷酸糖原的异生作用从丙酮酸转变为糖原的过程中,并非完全是糖酵解的逆反应,因为糖酵解过程中有三个激