On Nitroaryl Reductase Activities in Several<i>Clostridia</i>

Angermaier, L.; Simon, Helmut

doi:10.1515/bchm2.1983.364.2.1653

Cited by 32 publications

(14 citation statements)

References 5 publications

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“…3). Oxygen‐sensitive nitroreductases are found in Escherichia coli (Mason & Holtzman, 1975; Peterson et al , 1979) and several Clostridium strains (Angermaier & Simon, 1983). In addition, some enzymes like NADPH:cytochrome P450 reductase (Orna & Mason, 1989), ferredoxin:NADP + reductase (Anuseviĉius et al , 1997) and NADH:ubiquinone reductase (Bironaitè et al , 1991) also catalyze this type of reduction.…”

Section: Bacterial Nitroreductasesmentioning

confidence: 99%

Reduction of polynitroaromatic compounds: the bacterial nitroreductases

et al. 2008

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Most nitroaromatic compounds are toxic and mutagenic for living organisms, but some microorganisms have developed oxidative or reductive pathways to degrade or transform these compounds. Reductive pathways are based either on the reduction of the aromatic ring by hydride additions or on the reduction of the nitro groups to hydroxylamino and/or amino derivatives. Bacterial nitroreductases are flavoenzymes that catalyze the NAD(P)H-dependent reduction of the nitro groups on nitroaromatic and nitroheterocyclic compounds. Nitroreductases have raised a great interest due to their potential applications in bioremediation, biocatalysis, and biomedicine, especially in prodrug activation for chemotherapeutic cancer treatments. Different bacterial nitroreductases have been purified and their biochemical and kinetic parameters have been determined. The crystal structure of some nitroreductases have also been solved. However, the physiological role(s) of these enzymes remains unclear. Nitroreductase genes are widely spread within bacterial genomes, but are also found in archaea and some eukaryotic species. Although studies on regulation of nitroreductase gene expression are scarce, it seems that nitroreductase genes may be controlled by the MarRA and SoxRS regulatory systems that are involved in responses to several antibiotics and environmental chemical hazards and to specific oxidative stress conditions. This review covers the microbial distribution, types, biochemical properties, structure and regulation of the bacterial nitroreductases. The possible physiological functions and the biotechnological applications of these enzymes are also discussed.

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Section: Bacterial Nitroreductasesmentioning

confidence: 99%

Reduction of polynitroaromatic compounds: the bacterial nitroreductases

et al. 2008

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“…1). The enzymes that catalyze this reaction are known as oxygen sensitive (type II) nitroreductases and are found in bacteria such as Clostridium (9) and Escherichia coli (171).…”

Section: Chemistry Of Tntmentioning

confidence: 99%

Biological Degradation of 2,4,6-Trinitrotoluene

Esteve‐Núñez

Caballero

Ramos

2001

Microbiol Mol Biol Rev

421

287

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Nitroaromatic compounds are xenobiotics that have found multiple applications in the synthesis of foams, pharmaceuticals, pesticides, and explosives. These compounds are toxic and recalcitrant and are degraded relatively slowly in the environment by microorganisms. 2,4,6-Trinitrotoluene (TNT) is the most widely used nitroaromatic compound. Certain strains of Pseudomonas and fungi can use TNT as a nitrogen source through the removal of nitrogen as nitrite from TNT under aerobic conditions and the further reduction of the released nitrite to ammonium, which is incorporated into carbon skeletons. Phanerochaete chrysosporium and other fungi mineralize TNT under ligninolytic conditions by converting it into reduced TNT intermediates, which are excreted to the external milieu, where they are substrates for ligninolytic enzymes. Most if not all aerobic microorganisms reduce TNT to the corresponding amino derivatives via the formation of nitroso and hydroxylamine intermediates. Condensation of the latter compounds yields highly recalcitrant azoxytetranitrotoluenes. Anaerobic microorganisms can also degrade TNT through different pathways. One pathway, found in Desulfovibrio and Clostridium, involves reduction of TNT to triaminotoluene; subsequent steps are still not known. Some Clostridium species may reduce TNT to hydroxylaminodinitrotoluenes, which are then further metabolized. Another pathway has been described in Pseudomonas sp. strain JLR11 and involves nitrite release and further reduction to ammonium, with almost 85% of the N-TNT incorporated as organic N in the cells. It was recently reported that in this strain TNT can serve as a final electron acceptor in respiratory chains and that the reduction of TNT is coupled to ATP synthesis. In this review we also discuss a number of biotechnological applications of bacteria and fungi, including slurry reactors, composting, and land farming, to remove TNT from polluted soils. These treatments have been designed to achieve mineralization or reduction of TNT and immobilization of its amino derivatives on humic material. These approaches are highly efficient in removing TNT, and increasing amounts of research into the potential usefulness of phytoremediation, rhizophytoremediation, and transgenic plants with bacterial genes for TNT removal are being done

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“…Although the physiological role of these enzymes is unknown, two types of nitroreductases have been described according to their response to oxygen (Asnis, 1957;McCalla et al ., 1978;Bryant et al ., 1981). Oxygen-sensitive nitroreductases mediate single-electron transfers, producing nitro-anion free radicals that, in the presence of oxygen, can be rapidly reoxidized in a futile redox cycle through which superoxide is generated (Peterson et al ., 1979;Angermaier and Simon, 1983). Oxygen-insensitive nitroreductases are widely distributed in nature and are flavoproteins that have been suggested to mediate the sequential transfer of two electrons from NADH or NADPH to the nitro moiety of nitrosubstituted compounds (Bryant et al ., 1981).…”

Section: Introductionmentioning

confidence: 99%

PnrA, a new nitroreductase‐family enzyme in the TNT‐degrading strain Pseudomonas putida JLR11

Caballero

Lázaro

Ramos

et al. 2005

Environmental Microbiology

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Nitroreductases are a group of proteins that catalyse pyridine nucleotide-dependent reduction of nitroaromatics compounds, showing significant human health and environmental implications. In this study we have identified the nitroreductase-family enzymes PnrA and PnrB from the TNT-degrading strain Pseudomonas putida. The enzyme encoded by the pnrA gene was expressed in Escherichia coli, purified to homogeneity and shown to be a flavoprotein that used 2 mol of NADPH to reduce 1 mol of 2,4,6-trinitrotoluene (TNT) to 4-hydroxylamine-2,6-dinitrotoluene, using a ping-pong bi-bi mechanism. The PnrA enzyme also recognized as substrates as a number of other nitroaromatic compounds, i.e. 2,4-dinitrotoluene, 3-nitrotoluene, 3- and 4-nitrobenzoate, 3,5-dinitrobenzamide and 3,5-dinitroaniline expanding the substrates profile from previously described nitroreductases. However, TNT resulted to be the most efficient substrate examined according to the Vmax/Km parameter. Expression analysis of pnrA- and pnrB-mRNA isolated from cells growing on different nitrogen sources suggested that expression of both genes was constitutive and that its level of expression was relatively constant regardless of the growth substrate. This is in agreement with enzyme-specific activity determined with cells growing with different N-sources.

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On Nitroaryl Reductase Activities in SeveralClostridia

Cited by 32 publications

References 5 publications

Reduction of polynitroaromatic compounds: the bacterial nitroreductases

Reduction of polynitroaromatic compounds: the bacterial nitroreductases

Biological Degradation of 2,4,6-Trinitrotoluene

PnrA, a new nitroreductase‐family enzyme in the TNT‐degrading strain Pseudomonas putida JLR11

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