The diverse antioxidant systems of Helicobacter pylori.

Abstract

The gastric pathogen Helicobacter pylori induces a strong inflammatory host response, yet the bacterium maintains long-term persistence in the host. H. pylori combats oxidative stress via a battery of diverse activities, some of which are unique or newly described. In addition to using the well-studied bacterial oxidative stress resistance enzymes superoxide dismutase and catalase, H. pylori depends on a family of peroxiredoxins (alkylhydroperoxide reductase, bacterioferritin co-migratory protein and a thiol-peroxidase) that function to detoxify organic peroxides. Newly described antioxidant proteins include a soluble NADPH quinone reductase (MdaB) and an iron sequestering protein (NapA) that has dual roles - host inflammation stimulation and minimizing reactive oxygen species production within H. pylori. An H. pylori arginase attenuates host inflammation, a thioredoxin required as a reductant for many oxidative stress enzymes is also a chaperon, and some novel properties of KatA and AhpC were discovered. To repair oxidative DNA damage, H. pylori uses an endonuclease (Nth), DNA recombination pathways and a newly described type of bacterial MutS2 that specifically recognizes 8-oxoguanine. A methionine sulphoxide reductase (Msr) plays a role in reducing the overall oxidized protein content of the cell, although it specifically targets oxidized Met residues. H. pylori possess few stress regulator proteins, but the key roles of a ferric uptake regulator (Fur) and a post-transcriptional regulator CsrA in antioxidant protein expression are described. The roles of all of these antioxidant systems have been addressed by a targeted mutant analysis approach and almost all are shown to be important in host colonization. The described antioxidant systems in H. pylori are expected to be relevant to many bacterial-associated diseases, as genes for most of the enzymes carrying out the newly described roles are present in a number of pathogenic bacteria.

• Authors: Ge Wang, Praveen Alamuri, Robert J Maier
• Journal: Molecular microbiology (Mol Microbiol) Vol. 61 Issue 4 Pg. 847-60 (Aug 2006) ISSN: 0950-382X [Print] England
• PMID: 16879643 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Review)

Chemical References

• Antioxidants
• Bacterial Proteins

Topics

• Animals
• Antioxidants (metabolism)
• Bacterial Proteins (physiology)
• Helicobacter Infections (microbiology)
• Helicobacter pylori (chemistry, enzymology, metabolism)
• Humans
• Inflammation (microbiology)
• Oxidative Stress