A model for the activation of phosphodiesterase by calmoduling based on a conversion of inactive dimers to active monomers, derived from radiation inactivation studies J. Biol. Chem. (1981) 256, 11351–11355 has been re-examined using a simple probability argument. We conclude that the original model is not supported by the radiation inactivation studies, since our analysis of this model would predict that the rate of radiation inactivation of calmodulin-dependent phosphodiesterase activity be exactly twice that for the decay in total activity in marked contrast with the results obtained.
