Characterization of a cyclic nucleotide phosphodiesterase-deficient mutant in yeast.

A mutation (pde1) was detected by suppressor activity on the CYR3 mutation which caused cAMP requirement for growth at 35 degrees C by the alteration of cAMP-dependent protein kinase. The pde1 mutant produced a significantly reduced level of cyclic nucleotide phosphodiesterase activity when assayed with 500 microM cAMP. Two cyclic nucleotide phosphodiesterases, I and II, were identified. Approximate molecular weights of these enzymes were 60,000 and 110,000, and the apparent Km values were 100 and 0.4 microM, respectively. The pde1 mutant was deficient in phosphodiesterase I activity. The cells carrying the pde1 mutation accumulated several times over the intracellular cAMP found in wild type cells. Phosphodiesterase I was not essential for growth of yeast cells, but controlled the intracellular cAMP levels in wild type and various mutant strains.