The Inhibitory Effect of Phosphorylase a on the Activation of Glycogen Synthase Depends on the Type of Synthase Phosphatase
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The activity of glycogen synthase phosphatase in rat liver stems from the co-operation of two proteins, a cytosolic S-component and a glycogen-bound G-component. It is shown that both components possess synthase phosphatase activity. The G-component was partially purified from the enzyme-glycogen complex. Dissociative treatments, which increase the activity of phosphorylase phosphatase manyfold, substantially decrease the synthase phosphatase activity of the purified G-component. The specific inhibition of glycogen synthase phosphatase by phosphorylase a, originally observed in crude liver extracts, was investigated with purified liver synthase b and purified phosphorylase a. Synthase phosphatase is strongly inhibited, whether present in a dilute liver extract, in an isolated enzyme-glycogen complex, or as G-component purified therefrom. In contrast, the cytosolic S-component is insensitive to phosphorylase a. The activation of glycogen synthase in crude extracts of skeletal muscle is not affected by phosphorylase a from muscle or liver. Consequently we have studied the dephosphorylation of purified muscle glycogen synthase, previously phosphorylated with any of three protein kinases. Phosphorylase a strongly inhibits the dephosphorylation by the hepatic G-component, but not by the hepatic S-component or by a muscle extract. These observations show that the inhibitory effect of phosphorylase a on the activation of glycogen synthase depends on the type of synthase phosphatase.
Luo X, Zhang Y, Ruan X, Jiang X, Zhu L, Wang X Diabetes. 2011; 60(5):1435-45.
PMID: 21471512 PMC: 3292316. DOI: 10.2337/db10-1663.
Mutalik V, Venkatesh K Theor Biol Med Model. 2005; 2:19.
PMID: 15907212 PMC: 1180476. DOI: 10.1186/1742-4682-2-19.
Lerin C, Montell E, Nolasco T, Garcia-Rocha M, Guinovart J, Gomez-Foix A Biochem J. 2003; 378(Pt 3):1073-7.
PMID: 14651477 PMC: 1224012. DOI: 10.1042/BJ20030971.
Browne G, Delibegovic M, Keppens S, Stalmans W, Cohen P Biochem J. 2001; 360(Pt 2):449-59.
PMID: 11716774 PMC: 1222246. DOI: 10.1042/0264-6021:3600449.
Inhibition of glycogenolysis in primary rat hepatocytes by 1, 4-dideoxy-1,4-imino-D-arabinitol.
Andersen B, Rassov A, Westergaard N, Lundgren K Biochem J. 1999; 342 Pt 3:545-50.
PMID: 10477265 PMC: 1220495.