The effects of inhibitors and magnesium ions on the activity of the thermostable extracellular cAMP-Specific phosphodiesterase of <Emphasis Type="Italic">Physarum polycephalum</Emphasis> plasmodium

Plasmodium of myxomycete Physarum polycephalum produces cyclic nucleotide phosphodiesterase (PDE). The extracellular PDE is cAMP-specific and highly thermostable. This study demonstrates that the extracellular PDE of Ph. polycephalum is weakly inhibited by caffeine, isobutylmethylxantine and theophiline (type I mammalian PDE nonspecific inhibitors), dipyridamole (mammalian PDE5, PDE6, PDE8 and PDE10 inhibitors), and erythro-9-3-(2-hydroxynonyl)]-adenine (mammalian PDE2 inhibitor). The enzyme does not require Mg²⁺ for the activity. The results show that the Ph. polycephalum extracellular PDE differs from class I PDEs, represented by mammalian PDE1-PDE11, and, most likely, belongs to a poorly investigated class II PDEs.