title: Direct interaction of calmodulin antagonists with Ca2+/calmodulin-dependent cyclic nucleotide phosphodiesterase.
abstract: Trypsin-treated Ca2+/calmodulin-dependent phosphodiesterase (CA2+-PDE), which had lost its sensitivity to Ca2+-calmodulin, was inhibited by various calmodulin antagonists, trifluoperazine, chlorpromazine, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) and aminoalkyl chain analogues of W-7 (A-3, A-4, A-5, I-240, A-6, A-7). These inhibitory effects were less than those on calmodulin-activated Ca2+-PDE. The ability of these compounds to inhibit trypsin-treated Ca2+-PDE correlated well with the inhibitory effect on calmodulin-activated Ca2+-PDE. W-7 inhibited trypsin-treated Ca2+-PDE in a competitive fashion with respect to cyclic GMP and the Ki value was 300 microM. The inhibition of trypsin-treated Ca2+-PDE by W-7 (300 microM) or A-7 (100 microM) was overcome by the addition of excess calmodulin. Trypsin-treated Ca2+-PDE can bind to W-7-coupled cyanogen bromide-activated Sepharose 4B in the presence of 1 mM EGTA. These results suggest that Ca2+-PDE possesses a binding site for calmodulin antagonists and that the binding site for these antagonists on this enzyme may be structurally similar to the binding site on calmodulin itself.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002417:Cattle; D002846:Chromatography, Affinity; D003488:Cyanogen Bromide; D004789:Enzyme Activation; D009419:Nerve Tissue Proteins / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D009419:Nerve Tissue Proteins; D013449:Sulfonamides; D014268:Trifluoperazine; C017967:W 7; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D003488:Cyanogen Bromide