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Anaerobic Energy Metabolism

G-6-P. G-1-P. UDP-Glucose. F-6-P. FBP. Anaerobic Energy Metabolism. Pentose Phosphate. GLYCOGEN. GLUCOSE. MANNOSE. GALACTOSE. DHAP. G3P. FRUCTOSE. Glycogen. PO 4. Glucose-1-Phosphate. Glucose-6-Phosphate. Glycogen Breakdown. Phosphorylase and Debranching Enzyme.

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Anaerobic Energy Metabolism

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  1. G-6-P G-1-P UDP-Glucose F-6-P FBP Anaerobic Energy Metabolism Pentose Phosphate GLYCOGEN GLUCOSE MANNOSE GALACTOSE DHAP G3P FRUCTOSE

  2. Glycogen PO4 Glucose-1-Phosphate Glucose-6-Phosphate Glycogen Breakdown Phosphorylase and Debranching Enzyme Phosphoglucomutase Glucose Glycolysis Take home: Glycogen contributes glucose to glycolysis and to blood glucose (Liver)

  3. O O O O CH2OH CH2OH CH2OH HO-P-OH HO-P-OH O-P-OH HO-P-OH CH2OH O O O O O O HO O O O O HO HO Phosphorylase O Glucose-1-PO4 PHOSPHORYLYSIS

  4. Glycogen Phosphorylase C N Glycogen Storage Site Can accommodate on 4-5 sugars Pyridoxal 5’-PO4 at active sites N C

  5. Phosphorylase: A Homo Dimer - 2 AMP + 2 AMP + Cyclic AMP * More active PHOS A 2 ADP 2 H2O Phosphorylase Phosphatase Phosphorylase B Kinase Covalent 2 ATP 2 PO4 PHOS B Less Active Allosteric PHOS B Immediate More active Hormonal Regulation

  6. Debranching Enzyme Highly branched core Phosphorylase Phosphorylase Glycogen Limit Branch (14) transglycosylase + D-glucose

  7. Debranching Enzyme (14) transglycosylase H2O Straight Chain D-glucose

  8. Glycogen Synthesis Glycogen Synthesis Degradation Glucose-6-PO4 Glucose-1-PO4 UDP-Glucose

  9. GLYCOGEN SYNTHESIS • ACTIVATION OF D-GLUCOSE • GLYCOSYL TRANSFER • BRANCHING Textbook p434 Strategies p199

  10. GLYCOGEN SYNTHESIS ENZYMES • UDP-glucose pyrophosphorylase • forms UDP-glucose • Glycogen Synthase • major polymerizing enzyme • Amylo-(1,4-1,6)-transglycosylase • forms branches

  11. ACTIVATION UDP-GLUCOSE G-1-P + UTP UDP-GLUCOSE + PPi UDP-Glucose pyrophosphorylase 2 Pi

  12. Go’(kJ mol-1) ~0 Glucose 1-PO4 + UTP UDP-Glucose + PPi H2O + PPi 2 Pi -33.5 Glucose 1-PO4 + UTP + H2O UDP-Glucose + 2 Pi -33.5 Glycogen Glycogen Synthase Phosphorylase PPi UTP Activated glucose Glucose 1-PO4 UDP-Glucose UDP-glucose pyrophosphorylase The hydrolysis of pyrophosphate drives this reaction

  13. GLYCOSYL TRANSFER UDP NON-REDUCING END NEW

  14. Glycogenin Amylo-(1,4 1,6)-transglycosylase Cleave BRANCHING Branching Enzyme

  15. Glycogenin Branching Enzyme Amylo-(1,4 →1,6)-transglycosidase

  16. RECIPROCAL REGULATION TAKE HOME: DEGRADATION What activates glycogen degradation inactivates glycogen synthesis. SYNTHESIS What activates glycogen synthesis inactivates glycogen degradation

  17. PO4 PO4 PO4 PO4 Glycogen Phosphorylase a Glycogen synthase b H2O H2O ADP ADP Active Less Active ATP ATP Phosphorylase b Glycogen synthase a Active Less Active Glucose-6-PO4 Glucose-1-PO4 UDP-Glucose ATP turns off SYNTHESIS ATP turns on DEGRADATION

  18. Glycogen Synthase a (I form) 1. More active 2. Unaffected by Glucose 6-PO4 Glycogen Synthase b (D form) 1. Less active 2. Dependent on Glucose 6-PO4 In older terminology D and I referred to Glucose-6-PO4 dependent and independent forms of the enzyme

  19. 3 Principles of Allosteric Regulation in glycogen synthesis “b” form has a higher Km for UDP-glucose. Shuts off synthesis. G-6-P overcomes Km increase, activates “b” form. “a” form is always active and does not depend on G-6-P.

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