Regulation of Pathways Flashcards
What do high energy signals do?
The signal a slow down of glycolysis and the TCA cycle and turn on gluconeogenesis
What do low energy signals do?
They signal an increase in glycolysis and the TCA cycle.
List examples of common high energy signals?
ATP, NADH, citrate
There are many many more, each specific to a cycle
What are the high energy signals of glycolysis (specifically phosphofructokinase) ?
ATP and Citrate
What are the low energy signals of glycolysis (specifically phosphofructokinase) ?
AMP and ADP
What is the formula summary for glycolysis?
glucose + O2 –> 2 pyruvate + 2H2O
2 ATP are produced
Explain phosphofructokinase regulation.
- PFK is an allosteric enzyme with several regulatory sites
- ATP binds to PFK and lowers it’s affinity for Frc-6-P
- ADP relieves this inhibition by binding PFK and raising its affinity for Frc-6-P
- PFK has 4 subunits and each has binding sites for Frc-6-P, ADP, and ATP
What is the formula summary for TCA cycle?
2 pyr + 5O2 –> 6CO2 + 4H2O
Describe the regulation of PDH complex
- Kinase inhibits
- Phosphatase activates
(This is described as kinase regulation which is regulation by phosphorylation)
How is protein kinase activated?
ATP turns into ADP (deactivated PDH)
How is protein phosphatase activated?
H2O consumed, Pi released (activating PDH)
Protein kinase is activated by NADH (high energy signal)
List some high energy signals involved in TCA cycle
ATP
NADH
Citrate
Succinyl CoA
List some low energy signals involved in TCA cycle
ADP
AMP
NAD+
CoA
Describe the regulation of citrate synthase (OAA –> citrate)
Succinyl CoA and NADH inhibit citrate synthase (they are high energy signals)
Describe the regulation of isocitrate dehydrogenase (isocitrate –> alpha ketoglutarate)
- activated by ADP
- inhibited by NADH and ATP
- this is the rate limiting step in TCA
- CO2 loss
- NADH is being formed (NADPH if in cytosol) so this is OXIDATIVE PHOSPHORYLATION
if there is an inhibition of this step, there is a citrate buildup which inhibited PFK
