Activation of Phycomyces adenosine 3', 5'-monophosphate phosphodiesterase by blue light.

Cyclic AMP phosphodiesterase can be extracted from sporangiophores of $\text{Phycomyces}\text{blakesleeanus}$. Activity is enhanced by 1–10 μM FAD and FMN but not by riboflavin. Moderate intensity of blue light also activates the enzyme, especially in the presence of 1mM GTP. The enzyme must be extracted and stored in the absence of blue light for this result. Forty times the intensity of red light has no effect. This finding is consistent with the very sudden transient drop in cyclic AMP level upon light stimulation in the intact sporangiophore.