author_facet Korshunov, Sergei
Imlay, James A.
Korshunov, Sergei
Imlay, James A.
author Korshunov, Sergei
Imlay, James A.
spellingShingle Korshunov, Sergei
Imlay, James A.
Molecular Microbiology
Two sources of endogenous hydrogen peroxide in Escherichia coli
Molecular Biology
Microbiology
author_sort korshunov, sergei
spelling Korshunov, Sergei Imlay, James A. 0950-382X 1365-2958 Wiley Molecular Biology Microbiology http://dx.doi.org/10.1111/j.1365-2958.2010.07059.x <jats:title>Summary</jats:title><jats:p>Mechanisms of hydrogen peroxide generation in <jats:italic>Escherichia coli</jats:italic> were investigated using a strain lacking scavenging enzymes. Surprisingly, the deletion of many abundant flavoenzymes that are known to autoxidize <jats:italic>in vitro</jats:italic> did not substantially lessen overall H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> formation. However, H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>‐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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> upon aeration. This tendency is substantially suppressed by cytochrome oxidase. Thus cytochrome <jats:italic>d</jats:italic> oxidase, which is prevalent among anaerobes, may diminish intracellular H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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.</jats:p> Two sources of endogenous hydrogen peroxide in <i>Escherichia coli</i> Molecular Microbiology
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title Two sources of endogenous hydrogen peroxide in Escherichia coli
title_unstemmed Two sources of endogenous hydrogen peroxide in Escherichia coli
title_full Two sources of endogenous hydrogen peroxide in Escherichia coli
title_fullStr Two sources of endogenous hydrogen peroxide in Escherichia coli
title_full_unstemmed Two sources of endogenous hydrogen peroxide in Escherichia coli
title_short Two sources of endogenous hydrogen peroxide in Escherichia coli
title_sort two sources of endogenous hydrogen peroxide in <i>escherichia coli</i>
topic Molecular Biology
Microbiology
url http://dx.doi.org/10.1111/j.1365-2958.2010.07059.x
publishDate 2010
physical 1389-1401
description <jats:title>Summary</jats:title><jats:p>Mechanisms of hydrogen peroxide generation in <jats:italic>Escherichia coli</jats:italic> were investigated using a strain lacking scavenging enzymes. Surprisingly, the deletion of many abundant flavoenzymes that are known to autoxidize <jats:italic>in vitro</jats:italic> did not substantially lessen overall H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> formation. However, H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>‐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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> upon aeration. This tendency is substantially suppressed by cytochrome oxidase. Thus cytochrome <jats:italic>d</jats:italic> oxidase, which is prevalent among anaerobes, may diminish intracellular H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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.</jats:p>
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author Korshunov, Sergei, Imlay, James A.
author_facet Korshunov, Sergei, Imlay, James A., Korshunov, Sergei, Imlay, James A.
author_sort korshunov, sergei
container_issue 6
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description <jats:title>Summary</jats:title><jats:p>Mechanisms of hydrogen peroxide generation in <jats:italic>Escherichia coli</jats:italic> were investigated using a strain lacking scavenging enzymes. Surprisingly, the deletion of many abundant flavoenzymes that are known to autoxidize <jats:italic>in vitro</jats:italic> did not substantially lessen overall H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> formation. However, H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>‐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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> upon aeration. This tendency is substantially suppressed by cytochrome oxidase. Thus cytochrome <jats:italic>d</jats:italic> oxidase, which is prevalent among anaerobes, may diminish intracellular H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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.</jats:p>
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spelling Korshunov, Sergei Imlay, James A. 0950-382X 1365-2958 Wiley Molecular Biology Microbiology http://dx.doi.org/10.1111/j.1365-2958.2010.07059.x <jats:title>Summary</jats:title><jats:p>Mechanisms of hydrogen peroxide generation in <jats:italic>Escherichia coli</jats:italic> were investigated using a strain lacking scavenging enzymes. Surprisingly, the deletion of many abundant flavoenzymes that are known to autoxidize <jats:italic>in vitro</jats:italic> did not substantially lessen overall H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> formation. However, H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>‐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<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> upon aeration. This tendency is substantially suppressed by cytochrome oxidase. Thus cytochrome <jats:italic>d</jats:italic> oxidase, which is prevalent among anaerobes, may diminish intracellular H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> 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.</jats:p> Two sources of endogenous hydrogen peroxide in <i>Escherichia coli</i> Molecular Microbiology
spellingShingle Korshunov, Sergei, Imlay, James A., Molecular Microbiology, Two sources of endogenous hydrogen peroxide in Escherichia coli, Molecular Biology, Microbiology
title Two sources of endogenous hydrogen peroxide in Escherichia coli
title_full Two sources of endogenous hydrogen peroxide in Escherichia coli
title_fullStr Two sources of endogenous hydrogen peroxide in Escherichia coli
title_full_unstemmed Two sources of endogenous hydrogen peroxide in Escherichia coli
title_short Two sources of endogenous hydrogen peroxide in Escherichia coli
title_sort two sources of endogenous hydrogen peroxide in <i>escherichia coli</i>
title_unstemmed Two sources of endogenous hydrogen peroxide in Escherichia coli
topic Molecular Biology, Microbiology
url http://dx.doi.org/10.1111/j.1365-2958.2010.07059.x