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Glycolysis and Citric Acid Cycle Bridged via Pyruvate Dehydrogenase

Glycolysis and Citric Acid Cycle Bridged via Pyruvate Dehydrogenase. Glycolysis are Cytosolic Enzymes While Mitochondria Complete Respiration. Pyruvate is moved from the cytosol to the mitochondrion Matrix membrane permeability is critical . Citric Acid Entry Point: Acetyl CoA.

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Glycolysis and Citric Acid Cycle Bridged via Pyruvate Dehydrogenase

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  1. Glycolysis and Citric Acid Cycle Bridged via PyruvateDehydrogenase

  2. Glycolysis are Cytosolic Enzymes While Mitochondria Complete Respiration Pyruvate is moved from the cytosol to the mitochondrion Matrix membrane permeability is critical

  3. Citric Acid Entry Point: Acetyl CoA

  4. PyruvateDehydrogenase Complex

  5. PyruvateDehydrogenase Complex Complex 4-10 million daltons with 3 distinct enzymes Pyruvate dehydrogenase (30 nM diameter) electron micrograph

  6. Acetyl Coenzyme- A Formation from Pyruvate: Three Distinct Reactions Irreversible reaction coupling glycolysis and citric acid cycle Enzyme complex couples the reaction steps together What is the first reaction that looks iffy?

  7. Electron Sink Needed Thiamine pyrophosphate (TPP) pulls in electrons

  8. Step 1: E1 (PDH) DecarboxylatesPyruvate

  9. Step 2: E2 Oxidizes Hydroxyethyl- to Acetyl-Dihydrolipoamide-E2 What is the structure of lipoic acid? What reaction couples lipoic acid and lysine?

  10. Step 3: E2 Oxidizes Hydroxyethyl- to Acetyl-and Transfers Acetyl- to CoA

  11. Step 4-5: E3 Oxidizes Reduced Dihydrolipoamide and Reduces NAD+ Proteins tightly associated with FAD: Flavoproteins

  12. PyruvateDehydrogenase: a Multi-Enzyme Complex with 5 Cofactors: CoA, NAD+, Lipoamide, TPP and FAD

  13. Mechanism of Pyruvate → Acetyl CoA

  14. Transacetylase Core Structure (Red Balls) Each red ball represents 3 E2 subunits Each subunit contains three domains Transacetylase domain has three subunits (1 shown in red)

  15. Reaction Sites for Pyruvate Dehydrogenase Catalysis

  16. Reaction Sites for Pyruvate Dehydrogenase Catalysis Intermediate Order? Dihydrolipoamide, Acetyl CoA, Coenzyme A, FADH2,Acetylipoamide, Lipoamide, Pyruvate, Hydroxyethyl-TPP, and NADH

  17. Reaction Sites for Pyruvate Dehydrogenase Catalysis Intermediate Order? Dihydrolipoamide, Acetyl CoA, Coenzyme A, FADH2,Acetylipoamide, Lipoamide, Pyruvate, Hydroxyethyl-TPP, and NADH

  18. Pyruvate Dehydrogenase Component (E1) Deactivated via Phosphorylation

  19. High Energy Charge Down Regulates Pyruvate Dehydrogenase

  20. Arsenite Poisoning via Pyruvate Dehydrogenase Inhibition What step is inhibited by arsenite?

  21. Test Your Understanding Would you expect that thiamine thiazolone pyrophosphate is a potential pyruvate dehydrogenase competitive inhibitor for TPP?

  22. Chapter 18 Problems: 1-10

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