Two sources of endogenous hydrogen peroxide in <i>Escherichia coli</i>

Korshunov, Sergei; Imlay, James A.

doi:10.1111/j.1365-2958.2010.07059.x

Cited by 168 publications

(140 citation statements)

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“…These partially reduced oxygen species, such as hydrogen peroxide (H 2 O 2 ) and superoxide, can damage cellular components, leading to protein and DNA damage and even cell death (1). ROS are generated during aerobic growth through the oxidation of metabolic redox enzymes (2). Furthermore, ROS, such as H 2 O 2 , generated by exogenous sources can enter the cell through diffusion.…”

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confidence: 99%

Insights into the Function of a Second, Nonclassical Ahp Peroxidase, AhpA, in Oxidative Stress Resistance in Bacillus subtilis

et al. 2016

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Organisms growing aerobically generate reactive oxygen-containing molecules, such as hydrogen peroxide (H 2 O 2 ). These reactive oxygen molecules damage enzymes and DNA and may even cause cell death. In response, Bacillus subtilis produces at least nine potential peroxide-scavenging enzymes, two of which appear to be the primary enzymes responsible for detoxifying peroxides during vegetative growth: a catalase (encoded by katA) and an alkylhydroperoxide reductase (Ahp, encoded by ahpC). AhpC uses two redox-active cysteine residues to reduce peroxides to nontoxic molecules. A specialized thioredoxin-like protein, AhpF, is then required to restore oxidized AhpC back to its reduced state. Curiously, B. subtilis has two genes encoding Ahp: ahpC and ahpA. Although AhpC is well characterized, very little is known about AhpA. In fact, numerous bacterial species have multiple ahp genes; however, these additional Ahp proteins are generally uncharacterized. We seek to understand the role of AhpA in the bacterium's defense against toxic peroxide molecules in relation to the roles previously assigned to AhpC and catalase. Our results demonstrate that AhpA has catalytic activity similar to that of the primary enzyme, AhpC. Furthermore, our results suggest that a unique thioredoxin redox protein, AhpT, may reduce AhpA upon its oxidation by peroxides. However, unlike AhpC, which is expressed well during vegetative growth, our results suggest that AhpA is expressed primarily during postexponential growth. IMPORTANCEB. subtilis appears to produce nine enzymes designed to protect cells against peroxides; two belong to the Ahp class of peroxidases. These studies provide an initial characterization of one of these Ahp homologs and demonstrate that the two Ahp enzymes are not simply replicates of each other, suggesting that they instead are expressed at different times during growth of the cells. These results highlight the need to further study the Ahp homologs to better understand how they differ from one another and to identify their function, if any, in protection against oxidative stress. Through these studies, we may better understand why bacteria have multiple enzymes designed to scavenge peroxides and thus have a more accurate understanding of oxidative stress resistance.

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Insights into the Function of a Second, Nonclassical Ahp Peroxidase, AhpA, in Oxidative Stress Resistance in Bacillus subtilis

et al. 2016

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“…2 mM) than are heme or pyridoxamine cofactors, so the biosynthetic pathway processes about 3 M substrate/s. The H 2 O 2 thereby formed by aspartate oxidase contributes about 25% of the endogenous H 2 O 2 in E. coli (10).…”

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How Escherichia coli Tolerates Profuse Hydrogen Peroxide Formation by a Catabolic Pathway

Kumar

Imlay

2013

J Bacteriol

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When Escherichia coli grows on conventional substrates, it continuously generates 10 to 15 M/s intracellular H 2 O 2 through the accidental autoxidation of redox enzymes. Dosimetric analyses indicate that scavenging enzymes barely keep this H 2 O 2 below toxic levels. Therefore, it seemed potentially problematic that E. coli can synthesize a catabolic phenylethylamine oxidase that stoichiometrically generates H 2 O 2 . This study was undertaken to understand how E. coli tolerates the oxidative stress that must ensue. Measurements indicated that phenylethylamine-fed cells generate H 2 O 2 at 30 times the rate of glucose-fed cells. Two tolerance mechanisms were identified. First, in enclosed laboratory cultures, growth on phenylethylamine triggered induction of the OxyR H 2 O 2 stress response. Null mutants (⌬oxyR) that could not induce that response were unable to grow. This is the first demonstration that OxyR plays a role in protecting cells against endogenous H 2 O 2 . The critical element of the OxyR response was the induction of H 2 O 2 scavenging enzymes, since mutants that lacked NADH peroxidase (Ahp) grew poorly, and those that additionally lacked catalase did not grow at all. Other OxyR-controlled genes were expendable. Second, phenylethylamine oxidase is an unusual catabolic enzyme in that it is localized in the periplasm. Calculations showed that when cells grow in an open environment, virtually all of the oxidase-generated H 2 O 2 will diffuse across the outer membrane and be lost to the external world, rather than enter the cytoplasm where H 2 O 2 -sensitive enzymes are located. In this respect, the periplasmic compartmentalization of phenylethylamine oxidase serves the same purpose as the peroxisomal compartmentalization of oxidases in eukaryotic cells.

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“…Analogously, when the genes encoding these enzymes are deleted from the Escherichia coli genome, hydrogen peroxide is generated upon oxygenation and accumulates in the extracellular growth medium (9,10). Hydrogen peroxide is mainly produced in central carbon and energy metabolism by oxidases, including pyruvate oxidase (Pox), lactate oxidase (Lox), and NADH oxidases (Nox) (11).…”

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H ₂ O ₂ Production in Species of the Lactobacillus acidophilus Group: a Central Role for a Novel NADH-Dependent Flavin Reductase

Hertzberger

Arents

Dekker

et al. 2014

Appl Environ Microbiol

141

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e Hydrogen peroxide production is a well-known trait of many bacterial species associated with the human body. In the presence of oxygen, the probiotic lactic acid bacterium Lactobacillus johnsonii NCC 533 excretes up to 1 mM H 2 O 2 , inducing growth stagnation and cell death. Disruption of genes commonly assumed to be involved in H 2 O 2 production (e.g., pyruvate oxidase, NADH oxidase, and lactate oxidase) did not affect this. Here we describe the purification of a novel NADH-dependent flavin reductase encoded by two highly similar genes (LJ_0548 and LJ_0549) that are conserved in lactobacilli belonging to the Lactobacillus acidophilus group. The genes are predicted to encode two 20-kDa proteins containing flavin mononucleotide (FMN) reductase conserved domains. Reductase activity requires FMN, flavin adenine dinucleotide (FAD), or riboflavin and is specific for NADH and not NADPH. The K m for FMN is 30 ؎ 8 M, in accordance with its proposed in vivo role in H 2 O 2 production. Deletion of the encoding genes in L. johnsonii led to a 40-fold reduction of hydrogen peroxide formation. H 2 O 2 production in this mutant could only be restored by in trans complementation of both genes. Our work identifies a novel, conserved NADH-dependent flavin reductase that is prominently involved in H 2 O 2 production in L. johnsonii.

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Two sources of endogenous hydrogen peroxide in Escherichia coli

Cited by 168 publications

References 25 publications

Insights into the Function of a Second, Nonclassical Ahp Peroxidase, AhpA, in Oxidative Stress Resistance in Bacillus subtilis

Insights into the Function of a Second, Nonclassical Ahp Peroxidase, AhpA, in Oxidative Stress Resistance in Bacillus subtilis

How Escherichia coli Tolerates Profuse Hydrogen Peroxide Formation by a Catabolic Pathway

H ₂ O ₂ Production in Species of the Lactobacillus acidophilus Group: a Central Role for a Novel NADH-Dependent Flavin Reductase

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Two sources of endogenous hydrogen peroxide in Escherichia coli

Cited by 168 publications

References 25 publications

Insights into the Function of a Second, Nonclassical Ahp Peroxidase, AhpA, in Oxidative Stress Resistance in Bacillus subtilis

Insights into the Function of a Second, Nonclassical Ahp Peroxidase, AhpA, in Oxidative Stress Resistance in Bacillus subtilis

How Escherichia coli Tolerates Profuse Hydrogen Peroxide Formation by a Catabolic Pathway

H 2 O 2 Production in Species of the Lactobacillus acidophilus Group: a Central Role for a Novel NADH-Dependent Flavin Reductase

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H ₂ O ₂ Production in Species of the Lactobacillus acidophilus Group: a Central Role for a Novel NADH-Dependent Flavin Reductase