Characterization of 3': 5' -cyclic AMP phosphodiesterase in Klebsiella aerogenes and its role in substrate-accelerated death.

Cyclic AMP phosphodiesterase in Klebsiella aerogenes is a soluble cytoplasmic enzyme with an apparent Km of 0.9 mM and a pH optimum of 7.0. It was inhibited by EDTA, Mg2+ and other metal ions. The enzyme activity was inhibited or activated by some nucleotides but not by any metabolite except pyruvate. It was inhibited by the methylxanthines, caffeine, theophylline and methylisobutylxanthine. During starvation or substrate-accelerated death, the enzyme activity remained essentially constant. It is postulated that during substrate-accelerated death the enzyme acts as a drain on the cellular cyclic AMP levels. The cyclic nucleotide concentrations during substrate-accelerated death are proposed to be controlled directly by adenylate cyclase.