Cyclic AMP,phosphodiesterase, and spore activation inPhycomyces blakesleeanus

A soluble cyclic AMP phosphodiesterase was demonstrated in crude extracts ofPhycomyces spores. During an activating heat treatment of the spores the cyclic AMP phosphodiesterase activity was reduced to some 15% of its value in dormant spores. During early germination the activity slowly increased. No difference was found in the behavior of the enzyme from dormant and activated spores during gel filtration and anion exchange chromatography or in its sensitivity toward heat denaturation. After the spores were heated at different temperatures there was a coincidence between germination induction and cyclic AMP phosphodiesterase inactivation. 3-Isobutyl-1-methylxanthine induced an increase in both cyclic AMP concentration and trehalase activity in the spores and led to complete germination of the spores.