PHOSPHODIESTERASE ACTIVITY AND CYCLIC-AMP CONTENT DURING EARLY GERMINATION OF MUCOR-ROUXII SPORES

Incubation ofMucor rouxii spores in complex medium under aerobic conditions resulted in a very rapid transient increase in the level of soluble, low-Km cAMP phosphodiesterase. Maximum activity was reached after 2-4 min. Simultaneously, the cAMP content increased quickly, reproducing the profile exhibited by phosphodiesterase. Activation of the enzymein vitro by a cAMP-dependent phosphorylation process showed that its stimulation was minimal at those times when its activity was highest. The correlation between cellular cAMP content, phosphodiesterase activity, and sensitivity of the enzyme to activation by phosphorylation suggests that thein vivo regulation of phosphodiesterase activity by cAMP-dependent phosphorylation may be the mechanism for shutoff of the cAMP signal elicited by glucose. © 1990 Academic Press, Inc.