Discovery of a cAMP deaminase that quenches cyclic AMP-dependent regulation.
An enzyme of unknown function within the amidohydrolase superfamily was discovered to catalyze the hydrolysis of the universal second messenger, cyclic-3',5'-adenosine monophosphate (cAMP). The enzyme, which we have named CadD, is encoded by the human pathogenic bacterium Leptospira interrogans. Although CadD is annotated as an adenosine deaminase, the protein specifically deaminates cAMP to cyclic-3',5'-inosine monophosphate (cIMP) with a kcat/Km of 2.7 ± 0.4 × 10(5) M(-1) s(-1) and has no activity on adenosine, adenine, or 5'-adenosine monophosphate (AMP). This is the first identification of a deaminase specific for cAMP. Expression of CadD in Escherichia coli mimics the loss of adenylate cyclase in that it blocks growth on carbon sources that require the cAMP-CRP transcriptional activator complex for expression of the cognate genes. The cIMP reaction product cannot replace cAMP as the ligand for CRP binding to DNA in vitro and cIMP is a very poor competitor of cAMP activation of CRP for DNA binding. Transcriptional analyses indicate that CadD expression represses expression of several cAMP-CRP dependent genes. CadD adds a new activity to the cAMP metabolic network and may be a useful tool in intracellular study of cAMP-dependent processes.
Department of Chemistry, Texas A&M University , P.O. Box 30012, College Station, Texas 77843-3012, United States.
Alissa M
AM
Goble
Youjun
Y
Feng
Frank M
FM
Raushel
John E
JE
Cronan
D000225:Adenine; D000241:Adenosine; D000249:Adenosine Monophosphate; D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D002373:Cyclic AMP Receptor Protein / Q000235:genetics / Q000378:metabolism; D007289:Cyclic IMP / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D007700:Kinetics; D007921:Leptospira interrogans / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D009709:Nucleotide Deaminases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; C481662:crp protein, E coli; D007289:Cyclic IMP; D000249:Adenosine Monophosphate; D000242:Cyclic AMP; D009709:Nucleotide Deaminases; D000262:Adenylyl Cyclases; D000225:Adenine; D000241:Adenosine