cAMP levels and in situ measurement of adenylate cyclase and cAMP phosphodiesterase activities during yeast-to-hyphae transition in the dimorphic fungus Mucor rouxii.

Intracellular levels of cAMP and specific activities of adenylate cyclase and cAMP phosphodiesterase were measured during yeast-to-hyphae transition in the dimorphic fungus M. rouxii. Enzymatic activities were measured in permeabilized cells under conditions preventing protein dephosphorylation and proteolysis. A two-fold decrease in intracellular cAMP levels occurred shortly after exposure of the yeast to air quite before morphological changes became evident. Morphogenesis to hyphae after exposure to air was inhibited by the addition of 10 mM dibutyryl cAMP to the culture medium, and the yeast morphology was maintained for at least 24 hours. The decrease in cAMP levels that occurs shortly after exposure of yeast culture to air was mainly accounted for by variations in the state of activation of cAMP phosphodiesterase while the specific activity of adenylate cyclase did not vary significantly during yeast-to-hyphae transition.