Local Allosteric Control & Phosphorylase B

[Twitch]

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Just curious if someone could clarify/explain this further:

AMP activates Phosporylase b as an allosteric regulator in Glycogen Phospharylase Regulation

Does it phosphorylate it as well so it becomes Phosphorylase a (active) so it can break down glycogen? I'm having an issue with "activate" b (inactive) so glycogen will break down part of this equation.

Thanks!

👍

 

[agranulocytosis]

Just curious if someone could clarify/explain this further:

AMP activates Phosporylase b as an allosteric regulator in Glycogen Phospharylase Regulation

Does it phosphorylate it as well so it becomes Phosphorylase a (active) so it can break down glycogen? I'm having an issue with "activate" b (inactive) so glycogen will break down part of this equation.

Thanks!

👍

The way I thought about it was that phosphate bonds have high energy. That energy is used to activate everything. That means even an enzyme, a phosphorylase, will need to become phosphorylated (activated) so it can transfer that phosphate (energy) to degrade glycogen.

That activation is done by glycogen phosphorylase kinase, which is in turn activated by the AMP-dependent kinase, which is activated by the AMP.

 

[agranulocytosis]

Lippincott's Biochem sums it up pretty well in nice big pictures. Try using that book in your studies.

 

[pguin]

The way I thought about it was that phosphate bonds have high energy. That energy is used to activate everything. That means even an enzyme, a phosphorylase, will need to become phosphorylated (activated) so it can transfer that phosphate (energy) to degrade glycogen.

That activation is done by glycogen phosphorylase kinase, which is in turn activated by the AMP-dependent kinase, which is activated by the AMP.

This above part is AMP as an allosteric regulator.

However, I think the question was in regards to AMP's direct activity on Phosphorylase B. What happens (as I understand it) is that AMP binds to phosphorylase B and increases its activity level without phosphorylating it.

You have to remember that the B formation is still able to break down some glycogen (and can therefore produce enough glucose-1-phosphate for the cell during resting activity). The A formation just does it at a much quicker rate

 

[pguin]

Also, glucose-6-phosphate and ATP work the same way on Phosphorylase A, thereby slowing its activity rate without removing the phosphate