Activation/dephosphorylation of rabbit muscle glycogen synthase by the catalytic subunits of protein phosphatase-1 and 2A.
Glycogen synthase a was purified from rabbit skeletal muscle by a procedure involving heparin-Sepharose chromatography. Glycogen synthase a was phosphorylated by the catalytic subunit of cAMP-dependent protein kinase to give synthase b1. Dephosphorylation and activation of synthase b1 was investigated using the catalytic subunits of protein phosphatase-1 and 2A. The dephosphorylation and activation of synthase b1 was biphasic with a larger rate constant for the initial phase. Analysis of tryptic phosphopeptides of glycogen synthase during the course of dephosphorylation revealed a faster initial phosphate release from site-2 by both phosphatases comparing to sites-1a and 1b. Ligand effects on synthase phosphatase reactions were also studied. Spermine was found to inhibit protein phosphatase-1 activity and to stimulate type-2A phosphatase using synthase b1 as substrate.
Farkas
I
I
Department of Medical Chemistry, University Medical School, Debrecen, Hungary.
Tóth
B
B
Vereb
G
G
Csortos
C
C
Gergely
P
P
D000818:Animals; D002846:Chromatography, Affinity; D006006:Glycogen Synthase / Q000096:biosynthesis*; D008024:Ligands / Q000494:pharmacology; D009132:Muscles / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D011817:Rabbits; D013379:Substrate Specificity; D013997:Time Factors
D008024:Ligands; D006006:Glycogen Synthase; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1