1. 1. Glycogen synthase from rabbit skeletal muscle was phosphorylated by phosphorylase kinase to yield synthase b2. 2. 2. Dephosphorylation and activation of synthase b2 by the catalytic subunits of protein phosphatase-1 (PP-lc) and protein phosphatase-2A (PP-2Ac) was studied. The apparent Km of PP-1c and PP-2Ac were 3. 3.3 μM and 6.2 μM, respectively. The apparent Vmax of PP-lc was about two times larger than that of PP-2Ac. 4. 4. Ligands with phosphate moiety (AMP, glucose-6-P at high concentration) caused an inhibition in dephosphorylation by both phosphatases. Spermine inhibited the dephosphorylation by PP-lc and stimulated the action of PP-2Ac. Therefore it can be employed to distinguish the phosphatases using synthase b2 as substrate.
ASJC Scopus subject areas