CHEM 271 Lecture Notes - Lecture 19: Protein Phosphatase 1, Receptor Tyrosine Kinase, Phosphorylase Kinase
18 Dec 2015
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Document Summary
Regulation of glycogen synthesis and degradation by pp1. After a bout of exercise, muscle must shift from a glycogen-degrading mode to one of glycogen replenishment. A first step in this metabolic task is to shut down the phosphorylated proteins that stimulate glycogen breakdown. This task is accomplished by protein phosphatases that catalyze the hydrolysis of phosphorylated serine and threonine residues in proteins. Protein phosphatase 1 plays key roles in regulating glycogen metabolism (figure 21. 20). Pp1 inactivates phosphorylase a and phosphorylase kinase by dephosphorylating them. Pp1 decreases the rate of glycogen breakdown; it reverses the effects of the phosphorylation cascade. Moreover, pp1 also removes phosphoryl groups from glycogen synthase b to convert it into the much more active glycogen synthase a form. Pp1 is yet another molecular device for coordinating carbohydrate storage. The catalytic subunit of pp1 is a 37-kd single-domain protein. These regulatory subunits bringing together the phosphatase and its substrates in the context of a glycogen particle.
