title: cAMP-dependent protein kinases from the insect Ceratitis capitata.
abstract: Among the components of the two cyclic nucleotide system of Ceratitis capitata pharate adults, two cAMP-dependent protein kinase activities have been identified and purified through a sequence of chromatographic procedures. The properties of both protein kinases, A-1 and A-2, were studied and characterized in comparison with those of other sources. Protein kinase A-2 from Ceratitis capitata corresponds to type I from mammals mainly concerning about the dissociating effect of histones. Protein kinase A-2 exhibited a molecular weight of 39,000 in the presence of cAMP, whereas in the absence of the cyclic nucleotide two components of 80,000 and 159,000 were present and attributed to the forms RC and R2C2, respectively. Protein kinase activities A-1 and A-2 were markedly inhibited by increasing ionic strength whereas the activity (-cAMP/+cAMP) ratio for protein kinase A-2 increased versus NaCl concentration. Histones H1 and H2B were the best substrates for both A-1 and A-2 activities; the high mobility group of insect proteins (HMG) were also notably phosphorylated by A-2 preparation. Among the cyclic nucleotides assayed for the protein kinase activity A-2, cAMP induced a high activation at the lowest concentrations although high cAMP concentrations decreased the protein kinase activity, possibly through binding to the catalytic site. The protein kinase A-2 preparations exhibited a complex kinetics due to the presence of two forms with different affinity for ATP; these forms may be related to the aggregation properties of the enzyme.
mesh_terms: D000818:Animals; D002413:Cations, Divalent / Q000494:pharmacology; D002848:Chromatography, DEAE-Cellulose; D000242:Cyclic AMP / Q000302:isolation & purification*; D004175:Diptera / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D009994:Osmolar Concentration; D011494:Protein Kinases / Q000302:isolation & purification*; D013379:Substrate Specificity
chemical_list: D002413:Cations, Divalent; D000242:Cyclic AMP; D011494:Protein Kinases; D008274:Magnesium