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Figure Regulatory Mechanisms in Pyruvate Dehydrogenase and the TCA Cycle covalent modification of enzymes ex: phosphorylation of pyruvate dehydrogenase (non-covalent) product and feedback inhibition (e.g. by NADH, ATP, citrate) allosteric effectors (ADP/ATP, Ca++)
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Page 584
Glycolysis and TCA cycle: final accounting
• based on ~2.5 ATP/NADH and 1.5 ATP/FADH2• ~32 ATP/(glucose oxidized to 6CO2)
Text – Figures, pg. 584
Free Energies for TCA Reactions
• note necessity of low (i.e. large negative) G for citrate synthase to drive preceding malate dehydrogenase reaction. This results in low oxaloacetate concentration.
• large negative G steps are points of regulation.*
***
Figure 17-15
Regulatory Mechanisms in Pyruvate Dehydrogenase and the TCA Cycle
• covalent modification of enzymes ex: phosphorylation of pyruvate dehydrogenase
• (non-covalent) product and feedback inhibition (e.g. by NADH, ATP, citrate)
• allosteric effectors (ADP/ATP, Ca++)
Figure 17-16
Points of Regulation in the TCA Cycle
inhibition
activationText – Figure 17-16
Figure 17-17
TCA Cycle intermediates are a major source of molecules for other metabolic pathways
• note that several of the molecules look like amino acids, except for the absence of an -amino group
Text – Figure 17-17
Page 589
TCA Cycle intermediates are a major source of molecules for other metabolic pathways
ex: production of glutamate from -ketoglutarate
Production of some other amino acids by transamination reactions
ex: production of alanine and -ketoglutarate from glutamate and pyruvate
Page 589
Production of some other amino acids by transamination reactions
ex: production of aspartate and pyruvate from oxaloacetate and alanine
Page 590
The depletion of TCA cycle intermediates for use in other pathways must be offset by replenishing (anaplerotic) reactions, including pyruvate carboxylase.
Text – Figure, pg. 590