title: The isolation and characterization of cyclic nucleotide phosphodiesterases from Morris hepatoma 5123tc(h) and rat liver.
abstract: Four main phosphodiesterase (PDE) forms were resolved and partially purified from rat liver and Morris hepatoma 5123tc(h). The activities of the high Km cyclic nucleotide PDE (form II) in hepatoma were markedly reduced compared to liver, while the activities of the low Km cAMP PDE (form III) and low Km cyclic nucleotide PDE (form IV) in hepatoma were markedly higher than those of liver. The partially purified low Km cAMP PDE's (forms III and IV) from liver showed non-linear Lineweaver-Burk plots, whereas the same enzyme forms in hepatoma displayed linear kinetics. Activation of low Km cGMP PDE activity by calmodulin was found with form I in liver whereas in hepatoma form II was responsive to calmodulin.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000302:isolation & purification* / Q000378:metabolism; D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000302:isolation & purification* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008114:Liver Neoplasms, Experimental / Q000201:enzymology*; D008297:Male; D051381:Rats
chemical_list: D002147:Calmodulin; D007093:Imidazoles; C029899:imidazole; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D002118:Calcium