Purine catabolism in Bacillus subtilis

  • Saxild, Hans Henrik (Project Manager)
  • Beier, Lars (Project Participant)
  • Nygaard, Per (Project Participant)

    Project Details

    Description

    We have demonstrated that Bacillus subtilis is capable of degrading purine compounds and use the resulting ammonia as the sole source of nitrogen. The different types of purine bases are eventually converted to xanthine, which is then oxidized to uric acid. Uric acid is further degraded to urea and free ammonia. Urea can then be further degraded to produce more ammonia. The level of purine catabolic enzymes is repressed during growth on excess nitrogen (ammonia or glutamine). Under nitrogen limiting conditions the enzyme level increases many folds. At the moment two regulatory components have been found to participate in the nitrogen control of purine catabolic genes. GlnA is the enzyme glutamine synthetase and inactivation of this protein leads to partially derepressed expression of purine catabolic genes. TnrA is a transcriptional activator and inactivation of this protein results in a significant decrease in the induction of the catabolic enzymes. All the genes necessary for purine degradation have been identified. The genes are only induced during growth on a poor nitrogen source and when allantoic acid is present in the cell. The allantoic acid controlled induction is mediated by a transcriptional activator PucR.
    Progress in 1999 :
    We have investigated the function and regulation of yknA the gene encoding guanine deaminase (new name is gde) and this gene is regulated in the same way as the other purine catabolic genes. Deletion analysis of one of the PucR regulated promoters shows that the activation by TnrA is indirect in that TnrA was found only to regulate the level of PucR, which in turn was responsible for the final induction of the purine catabolic genes. Using genetics and bioinformatic means we were able to define the most likely DNA sequence recignized by PucR. We are now in the process of over expressing and purify the PucR protein.
    StatusFinished
    Effective start/end date01/01/199531/12/1999