10 – Glycolysis Flashcards
Phosphofructokinase 1 -PFK1
Gatekeeper of glycolysis
1st satge od metabolism
glycolysis
(first half = conversion of glucose to pyruvate)
2nd stage of metabolism
in mitochondria - citric acid cycle
3rd stage of metabolism
electorn transport chain
-use of electrons harvested in upstream glycolysis in CAC
-electorns are converted to a proton gradient across inner mitochondrial membrane
4th satge of emtabolism
proton gradient used to synthesize ATP
by ATP synthase
Glycolysis means
sugar breaking
-break sugar to 2 pyruvates
glycolysis Multi-step process
1.phosphorylate
2.change ring shape
3.phosphorylate again
4.smash to break into 2 individual pieces
5. individual pieces are converted downstream to pyruvate
6. oxidize/make NADH
(2 electrons are harvested)
7.dephosphorylate/make ATP
8.Mutate
9.condense - remove water molecule
10.dephosphorylate /make ATP
1st step of glycolysis =
pump-priming & generate useful metabolite that can form glycogen
what is prime pumping?
Need to spend a little ATP to make more
Think of it as water pumping
To prime pump = need to have water first
Spend a little water to get more water
what does it mean to prime pump?
think about the graph
NOT catalytic
looking at change of free energy of reactants, not at the height of transition state
-but increasing free energy of reactants
making a molecules with higher baseline amount of free energy that drives the forward reaction & increase rate
Glucose… is Performed by large machines
disassembly line
Cancer cells show increased…
glycolytic flux
-hyperactivation of glycolysis
Mutations in glycolytic enzymes found in patient tumors
Where does a cell WANT to control glycolysis?
Steps with big -ΔG = effectively irreversible
Can back up – but low probability
Too large of -ΔG = small chances to go back
-particularly steps in which ATP is hydrolyzed
(pump priming step, PFK1 step)
PFK1 performs
2nd phosphorylation – step 3
To reverse direction – have to synthesize ATP = very rare
PFK1 switches between
active & inactive states based on rates of rxn
entire tetramer changes conformation
PFK1 is an example of
allosteric enzyme
PFK1 Tense inactive state
Has inhibitor
Substrate binding site closed
PFK1 Relaxed active state
Inhibitor closed
Substrate binding site more open
Activators = bind to active site = stabilize it
Has 4 separate polypeptide chains
each capable of…
PFK1
Each capable of performing phosphorylation
model for allostery Explains hemoglobin
MWC model
how does MWC model work
hemoglobin can switch to fully occupied state with 4 oxygens or fully empty state
-If 1 ligand bounds = switch to active & rapidly fills up the tetramer
-if Lose oxygen = switch to inactive & rapidly dump all ocygen to tissue
PFK – inhibited by
its products : ATP & citrate
ATP & citrate – bind to PFK1 tetramer & snap into off state
-Cancer mutations block product inhibition
ATP = both
both substrate & inhibitor
high level of ATP = glycolysis shut down
ATP = 0 – enzyme cant work
If there is ATP = always off-state
PFK – activated directly by & Indirectly by
directly by AMP
-If starve ATP
-ADP –> AMP+ATP
Indirectly by excess fructose-6-phosphate
PFK1 – determines
rate of glycolytic flux
How do cells monitor their disassembly machines?
By conformational switching modulated by allosteric activators & inhibiting
