Linkage between toxin production and purine biosynthesis in Clostridium difficile

J Med Microbiol. 2002 Jan;51(1):34-41. doi: 10.1099/0022-1317-51-1-34.


The production of toxins A and B by Clostridium difficile was greatly enhanced under biotin-limited conditions, in which a 140-kDa protein was expressed strongly. Gene cloning revealed that this protein was a homologue of formylglycinamidine ribonucleotide synthetase (FGAM synthetase, EC, which is known as PurL in Escherichia coli and catalyses the fourth step of the de novo purine biosynthesis pathway. This enzyme consisted of a single polypeptide, although FGAM synthetases of gram-positive bacteria usually consist of two subunits. Inhibition of the enzymic activity of C. difficile PurL by O-diazoacetyl-L-serine (azaserine) resulted in enhanced toxin B production even in biotin-sufficient conditions. In contrast, blockade of the preceding step of the PurL catalysing step by sulfamethoxazole inhibited toxin B production almost completely. These results suggest that accumulation of formylglycinamide ribonucleotide (FGAR), a substrate of FGAM synthetase, enhances toxin production by C difficile and depletion of FGAR reduces toxin production.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Anti-Bacterial Agents / pharmacology
  • Azaserine / pharmacology
  • Bacterial Proteins / biosynthesis
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Toxins / biosynthesis*
  • Biotin / metabolism*
  • Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor / chemistry
  • Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor / genetics
  • Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor / metabolism
  • Clostridium difficile / drug effects
  • Clostridium difficile / metabolism*
  • Cytotoxins / biosynthesis
  • Enterotoxins / biosynthesis*
  • Escherichia coli Proteins*
  • Glycine / analogs & derivatives*
  • Glycine / chemistry
  • Glycine / metabolism
  • Humans
  • Ligases*
  • Molecular Sequence Data
  • Polymerase Chain Reaction
  • Purines / biosynthesis*
  • Ribonucleotides / chemistry
  • Ribonucleotides / metabolism
  • Sequence Homology
  • Sulfamethoxazole / pharmacology


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Bacterial Toxins
  • Cytotoxins
  • Enterotoxins
  • Escherichia coli Proteins
  • Purines
  • Ribonucleotides
  • tcdA protein, Clostridium difficile
  • toxB protein, Clostridium difficile
  • phosphoribosyl-N-formylglycineamide
  • Biotin
  • Azaserine
  • Ligases
  • Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor
  • PurL protein, E coli
  • phosphoribosylformylglycinamidine synthetase
  • Sulfamethoxazole
  • Glycine
  • purine

Associated data

  • GENBANK/AB047389