Caffeine Junkie: An Unprecedented Glutathione S-transferase-dependent Oxygenase Required for Caffeine Degradation by Pseudomonas Putida CBB5

J Bacteriol. 2013 Sep;195(17):3933-9. doi: 10.1128/JB.00585-13.

Abstract

Caffeine and other N-methylated xanthines are natural products found in many foods, beverages, and pharmaceuticals. Therefore, it is not surprising that bacteria have evolved to live on caffeine as a sole carbon and nitrogen source. The caffeine degradation pathway of Pseudomonas putida CBB5 utilizes an unprecedented glutathione-S-transferase-dependent Rieske oxygenase for demethylation of 7-methylxanthine to xanthine, the final step in caffeine N-demethylation. The gene coding this function is unusual, in that the iron-sulfur and non-heme iron domains that compose the normally functional Rieske oxygenase (RO) are encoded by separate proteins. The non-heme iron domain is located in the monooxygenase, ndmC, while the Rieske [2Fe-2S] domain is fused to the RO reductase gene, ndmD. This fusion, however, does not interfere with the interaction of the reductase with N1- and N3-demethylase RO oxygenases, which are involved in the initial reactions of caffeine degradation. We demonstrate that the N7-demethylation reaction absolutely requires a unique, tightly bound protein complex composed of NdmC, NdmD, and NdmE, a novel glutathione-S-transferase (GST). NdmE is proposed to function as a noncatalytic subunit that serves a structural role in the complexation of the oxygenase (NdmC) and Rieske domains (NdmD). Genome analyses found this gene organization of a split RO and GST gene cluster to occur more broadly, implying a larger function for RO-GST protein partners.

MeSH terms

  • Biotransformation
  • Caffeine / metabolism*
  • Carbon / metabolism
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • Gene Order
  • Glutathione Transferase / genetics
  • Glutathione Transferase / metabolism*
  • Molecular Sequence Data
  • Multigene Family
  • Nitrogen / metabolism
  • Oxygenases / genetics
  • Oxygenases / metabolism*
  • Pseudomonas putida / enzymology*
  • Pseudomonas putida / genetics
  • Pseudomonas putida / metabolism*
  • Sequence Analysis, DNA
  • Synteny

Substances

  • DNA, Bacterial
  • Caffeine
  • Carbon
  • Oxygenases
  • Glutathione Transferase
  • Nitrogen

Associated data

  • GENBANK/KC778191