Phosphorylation of rat heart glycogen synthase: studies in cardiomyocytes and in vitro phosphorylations with cAMP-dependent kinase and protein phosphatase-1
Graduate School of Biomedical Sciences; Department of Biochemistry and Molecular Pharmacology
Medical Subject Headings
Animals; Cyclic AMP; Glycogen Synthase; Immunologic Techniques; Myocardium; Peptide Fragments; Phosphoprotein Phosphatases; Phosphoproteins; Phosphorylation; Protein Kinases; Protein Phosphatase 1; Rats
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.
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Citation: Biochim Biophys Acta. 1987 Apr 2;928(1):98-106.
Biochimica et biophysica acta
Wolleben, Charles Daniel; McPherson, R. Kirk; Rulfs, Jill; Johnson, Gary L.; and Miller, Thomas B., "Phosphorylation of rat heart glycogen synthase: studies in cardiomyocytes and in vitro phosphorylations with cAMP-dependent kinase and protein phosphatase-1" (1987). GSBS Student Publications. 940.