Inhibition of Calmodulin‐Stimulated Phosphodiesterase Activity by Vasoactive Intestinal Peptide

Abstract
The effects of certain peptides of the glucagon family on calmodulin activity were determined from their capacity to inhibit a calmodulin‐dependent form of phosphodiesterase. Vasoactive intestinal peptide and secretin were potent inhibitors of calmodulin activity, having IC50 values of 0.5 μM and 2 μM, respectively. By contrast, glucagon failed to inhibit calmodulin activity even at concentrations of 100 μM. None of these compounds significantly inhibited the basal activity of phosphodiesterase at concentrations up to 100 μM. These findings support the suggestion that important structural features of peptides for anticalmodulin activity include a net positive charge and a hydrophobic surface.