Adenosine 3',5'-monophosphate phosphodiesterase in the growth medium of Physarum polycephalum.

The acellular slime mold Physarum polycephalum releases a soluble adenosine 3', 5'-monophosphate phosphodiesterase into the growth medium. Although this enzyme resembles the particulate diesterase of the same organism in kinetic properties and in inhibition by methyl purines, its greater stability, its insensitivity to stimulation by imidazole and to inhibition by adenosine triphosphate,- and its selective release into the medium indicate a specific function, perhaps protection against exogenous cyclic nucleotide, for the soluble enzyme.