Cetiedil inhibition of calmodulin-stimulated enzyme activity

Cetiedil, an in vitro anti-sickling agent, inhibited calmodulin-stimulated cyclic 3':5'-nucleotide phosphodiesterase (EC 3.1.4.17) and Ca2+-ATPase (ATP phosphohydrolase, EC 3.6.1.3) activities. The drug had no effect on basal enzyme activities in the absence of calmodulin. The inhibition of phosphodiesterase was competitive with respect to the concentrations of both cAMP and calmodulin. Cetiedil did not inhibit calmodulin-stimulated enzyme activities by acting as a calcium chelator, since increasing the concentration of calcium did not reverse the inhibitory effect.