title: Specificity of protein phosphatases in the dephosphorylation of protein kinase C.
abstract: Protein kinase C can autophosphorylate in vitro and has also been shown to be phosphorylated in vivo. In order to investigate the factors that may determine the phosphorylation state of protein kinase C in vivo, we determined the ability of the ATP + Mg2+-dependent phosphatase and the polycation-stimulated (PCS) phosphatases to dephosphorylate protein kinase C in vitro. These studies show that all the oligomeric forms of the PCS phosphatases (PCSH1, PCSH2, PCSM and PCSL phosphatases) are effective in the dephosphorylation of protein kinase C, showing 34-82% of the activity displayed with phosphorylase a as substrate. In contrast both the catalytic subunit of the PCS phosphatase and that of the ATP+Mg2+-dependent phosphatase showed only weak activity with protein kinase C as substrate. All these phosphatases, however, were activated by protamine (Ka 14-16 micrograms/ml) through what appears to be a substrate-directed effect. The relative role of these phosphatases in the control of protein kinase C is discussed.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D008274:Magnesium / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011073:Polyamines; D000071228:Polyelectrolytes; D011108:Polymers / Q000494:pharmacology; D011479:Protamines / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D011817:Rabbits; D013379:Substrate Specificity
chemical_list: D000255:Adenosine Triphosphate; D008274:Magnesium; D010749:Phosphoprotein Phosphatases; D011073:Polyamines; D000071228:Polyelectrolytes; D011108:Polymers; D011479:Protamines; D011493:Protein Kinase C