Effect of carbon sources on the rates of cyclic AMP synthesis, excretion, and degradation, and the ability to produce beta-galactosidase in Escherichia coli

Abstract

We have determined the rates of adenosine 3',5'-cyclic monophosphate (cAMP) synthesis, excretion, and degradation, and the cAMP pool size in Escherichia coli grown on various carbon sources. We have found that the cAMP pool size increases in approximate proportion to increases in the cAMP synthetic rate. Although the combined rate of excretion and degradation of cAMP is in approximate proportion to the cAMP pool size, no such regular relationship is seen between the cAMP pool size and either the excretion rate or the degradation rate. Using a method which we have developed for determining the cellular efficiency of enzyme production (termed 'cellular' rate), we have reexamined the relationship between cAMP pool size and the rate of beta-galactosidase production. Although there exists an overall trend of increasing rate of beta-galactosidase production with increasing cAMP pool size, large variations in the rates of beta-galactosidase production are seen even under culture conditions which yield similar cAMP pool sizes. This suggests that the intracellular level of cAMP cannot be the unique regulator of beta-galactosidase production.