Talk:Glycogen phosphorylase

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An expansion of the mechanism by which the enzyme breaks glycogen would be helpful. —Preceding unsigned comment added by Templemd (talk • contribs) 04:37, 7 November 2007 (UTC)

Glucagon vs. Adrenaline in the activation pathway
109.186.40.245 (talk) 11:15, 24 August 2010 (UTC) Glycogen is stored mainly in the liver and in muscle tissue. Epinephrine binds to the two differnet tissues via different receptors - Alpha 1 adrenergic receptor in the liver and Beta adrenergic receptor in the muscle. Binding of Epinephrine has different effects on the two tissues:

In the liver, epinephrine enhances glycogen breakdown via glycogen phosphorylase. This activity is mediated via PLC (which in turn is activated by Gq)by the conversion of phosphatidylinositol 4,5-bisphosphate into DAG and inositol 1,4,5-trisphosphate (IP3). IP3 then triggers Calcium influx from the ER, binding of Calcium to Calmodulin and activation of Calmodulin-dependent Glycogen Phosphorylase. Glucagon is responsible for cAMP rise via Gs( in Hepatocytes ) and controls Glycolysis and GNG, but not Glycogen breakdown.

In the Muscle, epinephrine (via Gs - Adenylate Cyclase) causes a cAMP rise which activates PKA that in turn activates Glycogen phosphorylase.

On the "Glycogen Phosphorylase" page this tissue difference is unclear, and one could assume that the liver has both types of receptors...
 * I must admit, I wasn't aware that adrenaline acted via α1 and Gq in the liver. With that in mind, perhaps it should also be explained in the article that adrenaline acts via this pathway, if it hasn't already been explained (I haven't read the whole article). I will revert my last edit, since it appears that the current information is not completely accurate and could become confusing, as you suggested.  Giftiger Wunsch   [TALK]  11:47, 24 August 2010 (UTC)

A question
The section mechanism says: "The protonated oxygen now represents a good leaving group, and the glycogen chain is separated from the terminal glycogen in an SN1 fashion, resulting in the formation of a glucose molecule with a secondary carbocation at the 1 position." The term glycogen is repeated twice. I wonder if the second glycogen should be glucose instead of glycogen.--Miguelferig (talk) 16:13, 29 August 2012 (UTC)

A correction needs to be made
The arrows in the mechanism figure are incorrect. In chemical mechanism, one moves electrons with curly arrows, not atoms. If I knew how to upload a png file, I would edit the page directly. I would like help making these changes. Davidbear61 (talk) 20:33, 8 June 2015 (UTC)