Original Papers

Archives of Microbiology

, Volume 152, Issue 2, pp 115-118

First online:

Pyrimidine, purine and nitrogen control of cytosine deaminase synthesis in Escherichia coli K12. Involvement of the glnLG and purR genes in the regulation of codA expression

  • Lennart AndersenAffiliated withInstitute of Biological Chemistry B, University of Copenhagen
  • , Mogens KilstrupAffiliated withInstitute of Biological Chemistry B, University of Copenhagen
  • , Jan NeuhardAffiliated withInstitute of Biological Chemistry B, University of Copenhagen

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Abstract

Cytosine deaminase, encoded by the codA gene in Escherichia coli catalyzes the deamination of cytosine to uracil and ammonia. Regulation of codA expression was studied by determining the level of cytosine deaminase in E. coli K12 grown in various defined media. Addition of either pyrimidine or purine nucleobases to the growth medium caused repressed enzyme levels, whereas growth on a poor nitrogen source such as proline resulted in derepression of cytosine deaminase synthesis. Derepression of codA expression was induced by starvation for either uracil or cytosine nucleotides. Nitrogen control was found to be mediated by the glnLG gene products, and purine repression required a functional purR gene product. Studies with strains harbouring multiple mutations affecting both pyrimidine, purine and nitrogen control revealed that the overall regulation of cytosine deaminase synthesis by the different metabolites is cumulative.

Key words

Escherichia coli codA glnLG purR Gene regulation Cytosine deaminase