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Title: The inhibitory effect of phosphorylase a on the activation of glycogen synthase depends on the type of synthase phosphatase
Authors: Mvumbi, Lelo ×
Doperé, F
Stalmans, Willy #
Issue Date: Sep-1983
Series Title: The Biochemical journal. vol:212 issue:2 pages:407-16
Abstract: 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.
ISSN: 0264-6021
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Department of Cellular and Molecular Medicine - miscellaneous
× corresponding author
# (joint) last author

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