Phosphorylation of rat heart glycogen synthase: studies in cardiomyocytes and in vitro phosphorylations with cAMP-dependent kinase and protein phosphatase-1

UMMS Affiliation

Graduate School of Biomedical Sciences; Department of Biochemistry and Molecular Pharmacology

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Life Sciences | Medicine and Health Sciences


The phosphorylation of glycogen synthase has been studied in freshly isolated adult rat cardiomyocytes. Six peaks of 32P-labeled tryptic peptides are recovered via C-18 high performance liquid chromatography (HPLC) when synthase is immunoprecipitated from 32P-labeled cardiomyocytes and digested with trypsin. When epinephrine treated cells are used as a source of enzyme, the same HPLC profile is obtained with a dramatic enhancement of 32P recovered in two of the HPLC peaks. In vitro phosphorylation of rat heart synthase by cAMP-dependent protein kinase stimulates the conversion of synthase from the I to the D form and results in the recovery of the same tryptic peptides from the C-18 as is the case for synthase derived from cardiomyocytes. Treatment of cAMP-dependent kinase phosphorylated synthase with protein phosphatase-1 leads to a reactivation of the enzyme and a dephosphorylation of the same tryptic peptides that are selectively phosphorylated in epinephrine treated cardiomyocytes. These results are discussed in relation to hormonal control of glycogen metabolism in cardiac tissue.


Biochim Biophys Acta. 1987 Apr 2;928(1):98-106.

Journal/Book/Conference Title

Biochimica et biophysica acta

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