Shuttle of Acetyl Groups to the Cytosol

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Shuttle of Acetyl Groups to the Cytosol
p779 Lehninger
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Glucose 6-Phosphate Dehydrogenase and
6-Phosphogluconate dehydrogenase Produce NADPH
p778 Lehninger
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Regulation of Lipid Metabolism

• Metabolic regulation is achieved by
• Hormonally stimulated phosphorylation-
• dephosphorylation of regulated enzymes
• Metabolic regulation by allosteric control
• Integrative aspects of regulation

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Key Regulatory Enzyme Acetyl CoA
Carboxylase BiotinAcetyl-CoA
ATP HCO3- Malonyl-CoA ADP Pi
H

• inactivated by phosphorylation (glucagon)
• activated by dephosphorylation (insulin)
• allosterically activated by citrate

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I. Hormonal Control with Glucagon

• Binding of the glucagon to the plasma membrane
  results in the subsequent phosphorylation of
  enzymes by protein kinases.
• a. Acetyl CoA carboxylase ( inhibited)
• b. Hormone sensitive lipase ( activated)
• c. Pyruvate dehydrogenase ( inhibited)
• With the following results
• a. Decreased fatty acid synthesis
• b. Increased gluconeogenesis
• c. Increased mobilization of stored fats