title: Calmodulin and Ca2+-dependent phosphorylation and dephosphorylation of 63-kDa subunit-containing bovine brain calmodulin-stimulated cyclic nucleotide phosphodiesterase isozyme.
abstract: Bovine brain contains calmodulin-dependent cyclic nucleotide phosphodiesterase isozymes which are composed of two distinct subunits: Mr 60,000 and 63,000. The 60-kDa but not the 63-kDa subunit-containing isozyme can be phosphorylated by cAMP-dependent protein kinase resulting in decreased affinity of this subunit toward calmodulin (Sharma, R. K., and Wang, J. H. (1985) Proc. Natl. Acad. Sci. U. S. A. 82, 2603-2607). In contrast, purified 63-kDa subunit-containing isozyme has been found to be phosphorylated by a preparation of bovine brain calmodulin-binding proteins in the presence of Ca2+ and calmodulin. The phosphorylation resulted in the maximal incorporation of 2 mol of phosphate/mol of the phosphodiesterase subunit with a 50% decrease in the enzyme affinity toward calmodulin. At a constant calmodulin concentration of 6 nM, the phosphorylated isozyme required a higher concentration of Ca2+ for activation than the nonphosphorylated phosphodiesterase. The Ca2+ concentrations at 50% activation by calmodulin of the nonphosphorylated and phosphorylated isozymes were 1.1 and 1.9 microM, respectively. Phosphorylation can be reversed by the calmodulin-dependent phosphatase, calcineurin, but not by phosphoprotein phosphatase 1. The results suggest that the Ca2+ sensitivities of brain calmodulin-dependent cyclic nucleotide phosphodiesterase isozymes can be modulated by protein phosphorylation and dephosphorylation mechanisms in response to different second messengers.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D002417:Cattle; D007527:Isoenzymes / Q000378:metabolism*; D046911:Macromolecular Substances; D008345:Manganese / Q000494:pharmacology; D008970:Molecular Weight; D009532:Nickel / Q000494:pharmacology; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D013997:Time Factors; D014357:Trypsin / Q000378:metabolism
chemical_list: D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D007527:Isoenzymes; D046911:Macromolecular Substances; D008345:Manganese; D009532:Nickel; D011494:Protein Kinases; D014357:Trypsin; D002118:Calcium