title: Some properties of adenosine 3',5'-cyclic monophosphate phosphodiesterase in the superior cervical ganglion of the guinea pig.
abstract: Adenosine 3',5'-cyclic monophosphate (cAMP) phosphodiesterase activity in crude guinea-pig superior cervical ganglion homogenates was assayed under a variety of experimental conditions. Two forms of cAMP phosphodiesterase were found, one with high and the other with low affinity for the substrate. The Km values were about 1 and 110 microM respectively. Imidazole slightly but constantly stimulated the former enzyme form over a wide range of concentrations and 1-methyl-3-isobutylxanthine was a weak competitive inhibitor with a Ki value of 90 microM. Low affinity cAMP phosphodiesterase activity was increased by calmodulin and Ca2+. This stimulation was not observed in the presence of trifluoperazine, a specific inhibitor of calmodulin. On the other hand, neither [D-Ala2]met-enkephalinamide nor prostaglandin E2, alone or in combination, influenced high affinity cAMP phosphodiesterase.
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D005728:Ganglia, Sympathetic / Q000201:enzymology*; D006168:Guinea Pigs; D007093:Imidazoles / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D007093:Imidazoles; D007527:Isoenzymes; D014268:Trifluoperazine; C029899:imidazole; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine