Role of adenosine 3',5'-cyclic monophosphate and its specific binding protein in the regulation of D-serine deaminase synthesis.

Adenosine 3',5'-cyclic monophosphate (cyAMP) and the cyAMP-binding protein are necessary for efficient induction of d-serine deaminase (Dsdase) synthesis in dsdC(+)dsdO(+) and dsdC dsdO(+) strains of Escherichia coli K-12, and for constitutive synthesis in dsdC dsdO(+) strains. Neither is required in dsdO strains, confirming previous indications that in dsdO mutants Dsdase synthesis is not subject to catabolite repression control. Since efficient Dsdase synthesis in dsdC(+) and dsdC strains that are dsdO(+) requires the cyAMP-binding protein, which acts at the level of transcription in other systems, it is concluded that catabolite repression acts at the level of transcription of the Dsdase structural gene. Since catabolite repression is reversed by the inducer, d-serine in dsdC dsdO(+) strains, it is concluded that induction also acts at the level of transcription in this system. The dsdC strains were found to be much more sensitive to induction by d-serine than are dsdC(+) strains under conditions of catabolite repression, whether the repression was caused by glucose or by loss of ability to form cyAMP or cyAMP-binding protein. This suggests that a d-serine-dsdC complex may be able to replace partially the cyAMP:cyAMP-binding protein action in initiation of Dsdase messenger ribonucleic acid synthesis-a positive control effect.