高中生物奥赛辅导生化——三羧酸循环.ppt

3.Aerobiccatalysisofcarbohydrateandtricarboxylicacidcycle第三节糖的有氧分解与三羧酸循环,丙酮酸脱羧，乙酰辅酶A的氧化均发生在线粒体的基质。,ATP的合成在线粒体的内膜上进行的,三羧酸循环（Tricarboxylicacidcycle)TCACycleKrebs循环（Krebscycle)柠檬酸循环（Citriccycle),3.1Asurveyofintroduction概述,GlucosePyruvateAcetal-CoATCACycle,NAD+,NADH+H+,CoA-SH,CO2,CO2+H2O,Glycolysis,Yieldingofacetyl-CoA,acetyl-CoAisoxidized,3.1.1葡萄糖的有氧分解包括三个部分,TheNobelPrizeinPhysiologyorMedicine1953,forhisdiscoveryofthecitricacidcycle,3.1.2三羧酸循环的研究简史,PyruvateisoxidizedandacetateistransferredtoCoA.AcetylCoAenterstheTCAcycle.AcetateisoxidizedtoCO2.,PyruvateisoxidizedandacetateistransferredtoCoA.AcetylCoAenterstheTCAcycle.AcetateisoxidizedtoCO2.,PyruvateisoxidizedandacetateistransferredtoCoA.AcetylCoAenterstheTCAcycle.AcetateisoxidizedtoCO2.,Pyruvateistransportedintomitochondria（线粒体）thenoxidizedtoacetyl-CoA(releasingCO2)beforeenteringthecitricacidcycle,3.2Pyruvateisoxidizedtoacetyl-CoA,丙酮酸脱氢酶系,Regulationofpyruvatedehydrogenasecomplex,砷化物对机体的毒害不仅限于糖酵解，它与丙酮酸脱氢酶复合物中E2辅基硫辛酰胺的巯基发生共价结合，使还原型硫辛酰胺形成失去催化能力的砷化物。,3.3.1Reactionprocessoftricarboxylicacidcycle(三羧酸循环,柠檬酸循环),3.3TricarboxylicAcidCycle,乙酰CoA,柠檬酸,顺乌头酸,异柠檬酸,a-酮戊二酸,琥珀酰CoA,琥珀酸,苹果酸,延胡索酸,草酰乙酸,乙酰CoA,柠檬酸,顺乌头酸,异柠檬酸,a-酮戊二酸,琥珀酰CoA,琥珀酸,苹果酸,延胡索酸,草酰乙酸,Thecyclebeginswiththecondensationofacetyle-CoAandoxaloacetatetoformcitrate,草酰乙酸,柠檬酸,柠檬酸合酶,Thehydrolysisthehighenergythioester(硫酯)drivesthereaction.,合酶(synthase)：催化加合反应，促使合成合成酶(synthetase)：催化连接反应，一般需要NTP,合酶与合成酶,G0=8.4kJ/mol,G0=-2.1kJ/mol,90%,4%,6%,Fluoridecitrate（氟柠檬酸）isthespecialinhbitorofaconitase,*,*,*,*,*,*,Citrateisomerizestoisocitrate(异柠檬酸)viacis-aconitate(顺乌头酸),Aconitase(乌头酸酶),Citrateisomerizestoisocitrateviacis-aconitate,酶活性中心的只能结合底物的一部分,底物的部分具有手性,分子局部的手性，即分子的前手性.,前手性、潜手性（pro-chiral),Reaction4and5,*,*,*,*,Isocitrateundergoesoxidativedecarboxylation(氧化脱羧)toforma-ketoglutarate(a-酮戊二酸),Isocitrateisoxidized(第一次脱氢)anddecarboxylated.(第一次脱羧),异柠檬酸脱氢酶,第二次脱氢,第二次脱羧.E1酶不受磷酸共价调节.ReactionrequiresTPPandlipoateetc(6种辅酶).,*,*,*,*,-ketoglutarateundergoesoxidativedecarboyxlationtoformsuccinyl-CoA(琥珀酰CoA),a-酮戊二酸脱氢酶系,*,*,琥珀酰CoA合成酶（也称琥珀酸硫激酶）,Cleavageofthethioesterbond(硫酯键)insuccinyl-CoAiscoupledtoGTP(orATP)formation,Thethirdexampleofsubstrate-levelphosphorylation.,琥珀酰CoA,琥珀酸,琥珀酸是对称分子,没有了手性.,琥珀酸,延胡索酸,Succinateisoxidizedtofumarate(延胡索酸),琥珀酸脱氢酶,ThefreeenergychangeofthisreactionisinsufficienttoreduceNAD+.SuccinateDehydrogenaseisdirectlylinkedwiththeelectrontransportchain.,立体异构体马来酸,丙二酸琥珀酸（丁二酸）,Succinateisoxidizedtofumarate(延胡索酸),1.Theenzymecatalyzesstereospecificdehydrogenation2.Malonate(丙二酸)istheinhibitorofthereaction,延胡索酸,苹果酸,FumarateishydratedtoL-malate(苹果酸),延胡索酸酶,Hydration(水合),*,*,*,*,or,Oxaloacetate(草酰乙酸)isregeneratedbytheoxidationofL-malate(苹果酸),Thestandardfreeenergyofthisreactionisverypositive.Theoxidationofmalateisdrivenbytheefficientremovaloftheproducts.,苹果酸脱氢酶,ThelastthreereactionsoftheoftheTCAcyclearesimilartofattyaciddegradationandsynthesis,andsomeaminoaciddegradations.oxidationhydrationoxidation.,Amethylenegroup(CH2)isconvertedtoacarbonylgroup(C=O).,ThelastthreereactionsoftheoftheTCAcycle,Detailsworkedoutbystudyinghighlypurifiedenzymesofthecycleinvitro;使用高度提纯的酶在体外实验证明了这一代谢途径Alsobyisotopetracerexperimentsinvivo;通过体内同位素示踪法也证明了这一代谢途径,ThecitricacidcyclewasconfirmedtobeuniversalincellsTCA循环被证明在细胞中是广泛存在的,1.总反应式:CH3-C-SCoA+3NAD+FAD+GDP+Pi2CO2+3NADHH+1FADH2+1GTP+CoA-SH,2.Therearetwocarbonatomsintheformofacetyl-SCoAenterseverycycle;andtherearetwodecarboxylationstakeplaceineachcycle;乙酰辅酶A中的二碳乙酰基进入TCA循环；在循环中发生两次脱羧反应.Notice:the2carbonatomsenteringthecyclearenotthesameasthoseleavingthecycle,3.3.2SurveyofTCAcycle,3.Therearefourdehydrogenationreactionstakeplaceineachcycle;在循环中发生四次脱氢反应(3NADH,1FADH2),4.Thereisasubstratelevelphosphoralation;循环中发生一次底物水平磷酸化,3.3.2SurveyofTCAcycle,5.Thereactionscatalyzedbyaconitaseandfumaraseisasymmetryreactions;顺乌头酸酶和延胡索酸酶等催化非对称反应6.Alloftheintermediarymetabolismsarenotsynthesisanddecompositionnet.所有中间代谢产物在代谢中没有净合成或净降解.,3.3.2SurveyofTCAcycle,1.Acetylinacetyl-S-CoAwasoxydized:化学氧化释放的自由能：874.9kJ/mol生物氧化释放的自由能：520.9kJ/mol用于ATP合成的自由能：354kJ/mol,3.4Theenergeticoftheaerobicdecompositionofglucose葡萄糖有氧分解途径的能量计算,2.HydrationsinTCA-cycle:,ThethirdH2OenteredinTCAcycle:,Citryl-CoA+H20succinyl-CoA+H2OFumarate+H20,Citrate+CoA-SHSuccidate+CoA-SHMatalte,H2O,H2O,3.4Theenergeticoftheaerobicdecompositionofglucose,H2O,3.Dehydrogenationsinoxydationofglucose:,3.4Theenergeticoftheaerobicdecompositionofglucose,4.Caculationofenergy,InEMP:,ATP4-2,NumbersofATP,2NADHH+22.5,Informationofacetyl-CoA:,2NADHH+22.5,InTCAcycle:,3NADHH+232.52,FADH2211.52,GTP2112,Summery:32,(FADH2),(21.5),(30),3.4Theenergeticoftheaerobicdecompositionofglucose,1.AllorganicchemicalscanbecompletelyoxidizedtoCO2andH2Oviaacycledpathway;所有的有机化合物都可以通过TCA环彻底降解为CO2和H2O;2.Plentyenergycanbeprovidedaccompanythecycledpathway;伴随着这一循环途径，大量的自由能被转换;,3.5TCA环的生理意义,3.Theintermediatesinthecycleareimportantsourcesforbiosyntheticprecursors;TCA环中的中间代谢产物是重要的生物合成的前体4.Thecycleisanamphibolicpathway,andisametabolichingeofallbiochemicalsTCA环是一个分解合成无定向途径，是所有生物化合物的代谢枢纽。分解产能,合成前体.,3.5TCA环的生理意义,Theylackthea-ketoglutaratedehydrogenase;厌氧菌缺乏a-酮戊二酸脱氢酶Precursorsareprovidedforthesynthesisofaminoacids,nucleotides,hemeetc.合成代谢的前体通过正向或逆向反应合成Useanincompletecitricacidcycleasasource,notofenergy,butofbiosyntheticprecursors.,厌氧细菌（anaerobicbacteria）中TCA环是中断的,TCA循环在合成代谢中的作用,合成其他物质的前体,必然导致草酰乙酸等浓度的降低,这使得乙酰CoA的受体大大减少,从而使TCA循环效率降低.,卟啉,3.6Reactionsthatreplenishcitricacidcycleintermediatesanapleroticreactions(TCA环的回补),增加草酰乙酸及苹果酸的数量,PEPPyruvateacetyl-CoA,oxaloacetate,CO2+ATP,ADP+Pi,CO2,GDP,GTP,Citrate,malate,NADH+H+,NAD+,丙酮酸羧化支路,Pyruvate,NADPH,Roleofbiotin(生物素)inthepyruvatecarboxylasereaction,Inadditiontogeneratingreducingpotential,theTCAcyc