title: Role of protein phosphatase 2C from bovine adrenal chromaffin cells in the dephosphorylation of phospho-serine 40 tyrosine hydroxylase.
abstract: Tyrosine hydroxylase (TH) is the rate-limiting enzyme in the synthesis of catecholamines. It is dephosphorylated by protein phosphatase (PP) 2A and PP2C. In this study we used a fixed amount of bacterially expressed rat TH (5 microM), phosphorylated only at serine 40 (pSer40TH), to determine the PP activities against this site that are present in extracts from the bovine adrenal cortex, adrenal medulla, adrenal chromaffin cells and rat striatum. We found that PP2C was the main TH phosphatase activity in extracts from the adrenal medulla and adrenal chromaffin cells. In adrenal cortex extracts PP2C and PP2A activities toward pSer40TH did not differ significantly. PP2A was the main TH phosphatase activity in extracts from rat striatum. Kinetic studies with extracts from adrenal chromaffin cells showed that when higher concentrations of pSer40TH (> 5 microM) were used the activity of PP2C increased more than the activity of PP2A. PP2C was maximally activated by 1.25 mM Mn2+ and by 5 mM Mg2+ but was inhibited by calcium. Our data suggest a more important role for PP2C than was previously suggested in the dephosphorylation of serine 40 on TH.
authors.affiliation: School of Biomedical Sciences and The Brain and Mental Health Research Program of the Hunter Medical Research Institute, Faculty of Health, University of Newcastle, Callaghan, New South Wales, Australia.
authors.forename: Lia R M
authors.initials: LR
authors.lastname: Bevilaqua
authors.forename: Martín
authors.initials: M
authors.lastname: Cammarota
authors.forename: Phillip W
authors.initials: PW
authors.lastname: Dickson
authors.forename: Alistair T R
authors.initials: AT
authors.lastname: Sim
authors.forename: Peter R
authors.initials: PR
authors.lastname: Dunkley
mesh_terms: D000302:Adrenal Cortex / Q000737:chemistry / Q000378:metabolism; D000313:Adrenal Medulla / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002457:Cell Extracts / Q000737:chemistry; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D003342:Corpus Striatum / Q000737:chemistry / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D000071636:Protein Phosphatase 2C; D012694:Serine / Q000378:metabolism; D013379:Substrate Specificity; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
chemical_list: D002457:Cell Extracts; D010710:Phosphates; D008345:Manganese; D012694:Serine; D014446:Tyrosine 3-Monooxygenase; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C; D008274:Magnesium; D002118:Calcium