One of the steps in the regulation of glycogen breakdown is the phosphorylation
ID: 161944 • Letter: O
Question
One of the steps in the regulation of glycogen breakdown is the phosphorylation of phosphorylase kinase by protein kinase A. Both the alpha and beta subunits of phosphorylase kinase become phosphorylated. Which of the following statements are correct concerning the role each of these reactions play in the regulation of phosphorylase kinase activity, and hence in the regulation of giycogen breakdown? (Check all that apply.) Phosphorylation of the alpha-subunit alone is necessary to activate phosphorylase kinase. Phosphorylation of the beta-subunit alone is necessary to activate phosphorylase kinase. Phosphorylation of the alpha-subunit is rapid, and phosphorylation of the beta-subunit is slow. Phosphorylation of the beta-subunit is rapid, and phosphorylation of the alpha-subunit is slow. Phosphorylation of the beta-subunit is necessary for protein phosphatase 1 to remove the phosphate group(s) from phosphorylase kinase and deactivate it. Phosphorylation of the alpha-subunit is necessary for protein phosphatase 1 to remove the phosphate groups) from phosphorylase kinase and deactivate it. Phosphorylation of the beta-subunit immediately deactivates phosphorylase kinase.Explanation / Answer
Answer is 6th one. Phosphorylase kinase is a Serine-Threonine protein kinase, that activates Glycogen Phosphorylase to release Glucose-1-Phosphate from Glycogen.
The enzyme is Butterfly shaped and contain four subunits. Those are a, b, r & d. The r subunit is catalytic site and all other sites are Regulatory sites.
In dephosphorylated condition, the a & b subunits, inhibits catalytic function of the enzymes. Upon phosphorylation of the both subunits, promotes its catalytic function and facilitates Glycogen breakdown. Phosphatase-1 dephoshprylation of a subunit inactivates enzyme
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