PortEco logo

PMID:20149100

From EcoliWiki
Jump to: navigation, search

Contents

Citation

Korshunov, S and Imlay, JA (2010) Two sources of endogenous hydrogen peroxide in Escherichia coli. Mol. Microbiol. 75:1389-401

Abstract

Mechanisms of hydrogen peroxide generation in Escherichia coli were investigated using a strain lacking scavenging enzymes. Surprisingly, the deletion of many abundant flavoenzymes that are known to autoxidize in vitro did not substantially lessen overall H(2)O(2) formation. However, H(2)O(2) production diminished by 25-30% when NadB turnover was eliminated. The flavin-dependent desaturating dehydrogenase, NadB uses fumarate as an electron acceptor in anaerobic cells. Experiments showed that aerobic NadB turnover depends upon its oxidation by molecular oxygen, with H(2)O(2) as a product. This reaction appears to be mechanistically adventitious. In contrast, most desaturating dehydrogenases are associated with the respiratory chain and deliver electrons to fumarate anaerobically or oxygen aerobically without the formation of toxic by-products. Presumably, NadB can persist as an H(2)O(2)-generating enzyme because its flux is limited. The anaerobic respiratory enzyme fumarate reductase uses a flavoprotein subunit that is homologous to NadB and accordingly forms substantial H(2)O(2) upon aeration. This tendency is substantially suppressed by cytochrome oxidase. Thus cytochrome d oxidase, which is prevalent among anaerobes, may diminish intracellular H(2)O(2) formation by the anaerobic respiratory chain, whenever these organisms encounter oxygen. These two examples reveal biochemical and physiological arrangements through which evolution has minimized the rate of intracellular oxidant formation.

Links

PubMed PMC3049997 Online version:10.1111/j.1365-2958.2010.07059.x

Keywords

Aerobiosis; Amino Acid Oxidoreductases/genetics; Amino Acid Oxidoreductases/metabolism; Cytochromes/metabolism; Electron Transport Chain Complex Proteins/metabolism; Escherichia coli/metabolism; Escherichia coli Proteins/metabolism; Fumarates/metabolism; Hydrogen Peroxide/metabolism; Metabolic Networks and Pathways; Models, Biological; Oxidoreductases/metabolism; Succinate Dehydrogenase/metabolism

Significance

You can help EcoliWiki by summarizing why this paper is useful

Useful Materials and Methods

You can help Ecoliwiki by describing the useful materials (strains, plasmids, antibodies, etc) described in this paper.

Annotations

Gene product Qualifier GO ID GO term name Evidence Code with/from Aspect Notes Status

EcoliWiki Links

Add links to pages that link here (e.g. gene, product, method pages)

See also

References

See Help:References for how to manage references in EcoliWiki.