TCA CentralityGlucose Citric acid cycle (TCA cycle; Krebs cycle) isGhycolysisa central pathwayPyruvate Multiple pathways feed into and from itCO2Amphibolic2eAcetyl CoARelates to both catabolism and anabolism Cyclic metabolic pathwayCitricacidGlycolysis; gluconeogenesis; pentosecydle2CO2ATphosphate are linearthe significance of this ?86
TCA Centrality Citric acid cycle (TCA cycle; Krebs cycle) is a central pathway • Multiple pathways feed into and from it Amphibolic • Relates to both catabolism and anabolism Cyclic metabolic pathway • Glycolysis; gluconeogenesis; pentose phosphate are linear • the significance of this ?
Entry into the TCA Cycle· Pyruvate produced by glycolysis is a significant source of acetyl-CoAfortheTCAcycle.? In eukaryotic cells, glycolysis occurs in the cytoplasm, whereas theTCA cycle reactions take place in the mitochondria, pyruvate mustfirst enter the mitochondria to enter the TCA cycle.: The oxidative decarboxylation of pyruvate to acetyl-CoA is theconnecting link between glycolysis and the TCA cycle. The reactionis catalyzed by pyruvate dehydrogenase, a multienzyme complex.Pyruvate + CoA +NAD+→acetyl-CoA +CO,+ NADH
Entry into the TCA Cycle • Pyruvate produced by glycolysis is a significant source of acetyl-CoA for the TCA cycle. • In eukaryotic cells, glycolysis occurs in the cytoplasm, whereas the TCA cycle reactions take place in the mitochondria, pyruvate must first enter the mitochondria to enter the TCA cycle. • The oxidative decarboxylation of pyruvate to acetyl-CoA is the connecting link between glycolysis and the TCA cycle. The reaction is catalyzed by pyruvate dehydrogenase, a multienzyme complex
Pyruvate+CoA+NAD+→Acetyl-CoA+CO2+NADHHN—CH2CHCH2[paenta'enik]CH2adj.泛酸的Transition stepNHPantothenic Pyruvate dehydrogenase complexacid residueCHOH>OxidativedecarboxylationofpyruvateH;CCHAdenosincCH> Transfer of acetyl unit to coenzyme A (CoA)> Traffic directorto control flow of 2-C units fromglycolysis into TCAcycleCoenzyme A (CoA)(a)CoenzymeA(CoA)containsa residueofpantothenicacid(pantothenate),alsoknownasvitaminBs.Thesulfhydrylgroupisthesiteofattachmentofothergroups
Transition step Pyruvate dehydrogenase complex Oxidative decarboxylation of pyruvate Transfer of acetyl unit to coenzyme A (CoA) Traffic director to control flow of 2-C units from glycolysis into TCA cycle [pæntə‘θenɪk] adj.泛酸的
Transition stepPyruvate dehydrogenase complexComplexof3enzymesandseveralcoenzymes.Located in mitochondrion Pyruvate (glycolysis) must move from cytosol tomitochondrionONAmatrTmerrgronetermemeronsoACFopurtioncristsF,portioe
Transition step Pyruvate dehydrogenase complex • Complex of 3 enzymes and several coenzymes • Located in mitochondrion • Pyruvate (glycolysis) must move from cytosol to mitochondrion
Pyruvate dehydrogenase complex (PDC)·ThePDC is formed from multiple copies of three enzymes·pyruvatedehydrogenase(El,丙酮酸脱氢酶)dihydrolipoamideacetyltransferase（E2，二氢硫辛酰胺乙酰转移酶）·dihydrolipoamidedehydrogenase(E3，二氢硫辛酰胺脱氢酶）: It contains five different coenzymes.: The active sites of all three enzymes are not far from one another, and the product ofthe first enzyme is passed directly to the second enzyme, and so on, without diffusionof substrates and products through the solution.· Eukaryotic PDC, one of the largest-known multienzyme complexes is a 9.5-megadalton (MD) assembly organized structure
Pyruvate dehydrogenase complex (PDC) • The PDC is formed from multiple copies of three enzymes: • pyruvate dehydrogenase (E1, 丙酮酸脱氢酶) • dihydrolipoamide acetyltransferase (E2, 二氢硫辛酰胺乙酰转移酶) • dihydrolipoamide dehydrogenase (E3, 二氢硫辛酰胺脱氢酶). • It contains five different coenzymes. • The active sites of all three enzymes are not far from one another, and the product of the first enzyme is passed directly to the second enzyme, and so on, without diffusion of substrates and products through the solution. • Eukaryotic PDC, one of the largest-known multienzyme complexes is a 9.5- megadalton (MD) assembly organized structure