Protein Phosphorylation and Regulation of Glycogen Metabolism

Glycogen synthase is regulated via the same pathway. Glycogen synthase is inactive in the phosphorylated form whereas in the dephosphorylated form, it is active. Three key enzymes of glycogen metabohsm are thus controlled with the help of reversible protein phosphorylation. 

Ca brings about its regulatory effect at the level of phosphorylase kinase. Phosphorylase kinase is activated by Ca. Ca influx comes into play particularly in contraction of muscle, a process by which Ca is released from storage and activates phosphorylase kinase. 

The basis of regulation of protein phosphatase I is the abUity of the catalytic subunit of the enzyme to reversibly associate with corresponding regulatory proteins. As a result, the activity and specificity of the enzyme are modulated. 

Glycogen-associated Proteins, G Snbnnit of Protein Phosphatase I 

The catalytic subimit of protein phosphatase I is associated with a glycogen binding protein, also known as the G submit of protein phosphatase I (Fig. 7.20). The G subunit is tightly bound to glycogen. Association of the catalytic subimit with the G subunit creates a form of protein phosphatase I known as protein phosphatase I-G 

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