title: Subunit A of calmodulin-dependent protein phosphatase requires Mn2+ for activity.
abstract: Bovine brain calmodulin-dependent protein phosphatase comprises a catalytic subunit A (Mr 60,000) and a regulatory subunit B (Mr 19,000). The native enzyme was active with Ca2+ or Mn2+. Upon resolution into its subunits in 6 M urea and 15 mM EDTA, subunit A was active with Mn2+; Co2+ and Ni2+ partially substituted for Mn2+, but Ca2+, Mg2+ and Zn2+ were ineffective. The stimulating effect of Mn2+ was not easily reversed by EGTA. Like the native phosphatase, subunit A was markedly stimulated by calmodulin or by controlled trypsinization. Unlike the native enzyme, however, trypsinized subunit A still required Mn2+ for activity. These findings provide evidence that the catalytic subunit of phosphatase may be a metallo (possibly Mn2+) enzyme.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D002147:Calmodulin / Q000494:pharmacology*; D002148:Calmodulin-Binding Proteins; D002413:Cations, Divalent; D002417:Cattle; D002712:Chlorides; D007700:Kinetics; D046911:Macromolecular Substances; D008345:Manganese / Q000494:pharmacology*; D017895:Manganese Compounds; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D002413:Cations, Divalent; D002712:Chlorides; D046911:Macromolecular Substances; D017895:Manganese Compounds; D008345:Manganese; D010749:Phosphoprotein Phosphatases; C025340:manganese chloride