title: Isoelectric-focusing patterns of cyclic nucleotide phosphodiesterase from rat heart.
abstract: 1. Isoelectric focusing on a flat gel bed of the rat heart cytosolic fraction resolved cyclic nucleotide phosphodiesterase activity into several forms, characterized by their substrate specificity, kinetic constants and dependence towards Ca2+ and calmodulin. A peak of pI 4.9 displayed 20 times more affinity for cyclic GMP than for cyclic AMP and was markedly inhibited by EGTA. A less substrate-specific form, only slightly sensitive to EGTA inhibition, focused at pH 5.45. Several overlapping peaks detected between pH 5.55 and pH6 specifically hydrolysed cyclic AMP, with non-Michaelian kinetics; these peaks were insensitive to Ca2+ chelation. 2. Isoelectric focusing did not dissociate enzyme-calmodulin complexes, as none of the resulting peaks was activatable by calmodulin plus Ca2+. 3. Some new information on rat cardiac phosphodiesterase is obtained with this technique, which is convenient for routine analytical studies of phosphodiesterase, as well as for preparative purposes.
mesh_terms: D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D007525:Isoelectric Focusing; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity
chemical_list: D007527:Isoenzymes; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases; D010727:Phosphoric Diester Hydrolases; D002118:Calcium