A novel pathway for the biodegradation of 3-nitrotoluene in Pseudomonas putida

Ali-Sadat, Shadan; Mohan, K. S.; Walia, Sandeep

doi:10.1111/j.1574-6941.1995.tb00140.x

Cited by 20 publications

(5 citation statements)

References 25 publications

(23 reference statements)

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“…Corresponding observations for the TOL-encoded benzyl alcohol dehydrogenase and benzaldehyde dehydrogenase have been reported by Delgado et al (7). Recent investigations have demonstrated reductive as well as oxidative initial attack during 3-NT metabolism in Pseudomonas putida OU83 (1). While 70% of the substrate was reduced to 3-aminotoluene, a minor part (30%) was converted, via 3-nitrobenzylalcohol, 3-nitrobenzaldehyde, and 3-nitrobenzoic acid, to 3-nitrophenol.…”

supporting

confidence: 70%

A New 4-Nitrotoluene Degradation Pathway in a Mycobacterium Strain

Spiess

Desiere

Fischer

et al. 1998

Appl Environ Microbiol

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Mycobacterium sp. strain HL 4-NT-1, isolated from a mixed soil sample from the Stuttgart area, utilized 4-nitrotoluene as the sole source of nitrogen, carbon, and energy. Under aerobic conditions, resting cells of the Mycobacterium strain metabolized 4-nitrotoluene with concomitant release of small amounts of ammonia; under anaerobic conditions, 4-nitrotoluene was completely converted to 6-amino-m-cresol. 4-Hydroxylaminotoluene was converted to 6-amino-m-cresol by cell extracts and thus could be confirmed as the initial metabolite in the degradative pathway. This enzymatic equivalent to the acid-catalyzed Bamberger rearrangement requires neither cofactors nor oxygen. In the same crucial enzymatic step, the homologous substrate hydroxylaminobenzene was rearranged to 2-aminophenol. Abiotic oxidative dimerization of 6-amino-m-cresol, observed during growth of theMycobacterium strain, yielded a yellow dihydrophenoxazinone. Another yellow metabolite (λmax, 385 nm) was tentatively identified as 2-amino-5-methylmuconic semialdehyde, formed from 6-amino-m-cresol bymeta ring cleavage.

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supporting

confidence: 70%

A New 4-Nitrotoluene Degradation Pathway in a Mycobacterium Strain

Spiess

Desiere

Fischer

et al. 1998

Appl Environ Microbiol

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“…Since there are various ways by which enzymes might become available for recruitment, more than one novel pathway might be patched together from promiscuous enzymes in a single bacterium. Indeed, Pseudmonas putida OU83 transforms 3-nitrotoluene via two routes25; 70% is reduced to 3-aminotoluene, and 30% is converted to 3-nitrophenol, from which the nitro group is removed by an unidentified process.…”

Section: Recruitment Of Promiscuous Enzymes To Serve New Functionsmentioning

confidence: 99%

Evolution of efficient pathways for degradation of anthropogenic chemicals

2009

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Anthropogenic compounds used as pesticides, solvents, and explosives often persist in the environment and can cause toxicity to humans and wildlife. The persistence of anthropogenic compounds is due to their recent introduction into the environment; microbes in soil and water have had relatively little time to evolve efficient mechanisms for degradation of these novel compounds. Some anthropogenic compounds are easily degraded, while others are degraded very slowly or only partially, leading to accumulation of toxic products. This review examines the factors that affect the ability of microbes to degrade anthropogenic compounds and the mechanisms by which novel pathways emerge in nature. New approaches for engineering microbes with enhanced degradative abilities include assembly of pathways using enzymes from multiple organisms, directed evolution of inefficient enzymes, and genome shuffling to improve microbial fitness under the challenging conditions posed by contaminated environments.Anthropogenic chemicals are widely used in agriculture, industry, medicine, and military operations. Examples include pesticides such as atrazine, pentachorophenol (PCP), 1,3-dichloropropene, and DDT, explosives such as trinitrotoluene (TNT), solvents such as trichloroethylene, and dielectric fluids such as PCBs. There was little concern over the fate of anthropogenic chemicals in the environment until the late 20 th century. Adverse effects on wildlife eventually focused attention on the fact that some anthropogenic chemicals persist in the environment because they are not readily degraded by microbes. However, some anthropogenic compounds, such as atrazine, are degraded remarkably quickly. Others, such as paraoxon, are efficiently detoxified, although not degraded. This review will examine how microbes assemble novel pathways for detoxification or degradation of anthropogenic compounds and how the efficiency of biodegradation can be enhanced by optimizing naturally occurring pathways and by patching together novel pathways using enzymes from different organisms.Microbial enzymes that act upon anthropogenic compounds arise from promiscuous activities of previously existing enzymes. Promiscuous enzymes can evolve to become more effective catalysts as a result of selective pressure for detoxification of a toxic compound or use of a novel source of carbon, nitrogen, or phosphorus. Detoxification often requires only a single step. For example, PCP is toxic because it dissipates trans-membrane proton gradients, and thereby uncouples oxidative phosphorylation 1,2 . Phanerochaete chrysosporium detoxifies PCP by methylating the hydroxyl group, thus eliminating its ability to transport protons across a lipid bilayer 3 . Figure 1. Atrazine is the most widely used pesticide in the world. Three steps that replace the substituents on the ring with hydroxyl groups convert atrazine into cyanuric acid, which is readily metabolized, either within the same microbe (e.g. Pseudomonas sp. strain ADP), or by other microbes. 4 PCP is used pri...

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“…Furthermore, the solvent tolerance of P. putida DOT-T1E might be exploited to enlarge the spectrum of solvents applicable for in situ product extraction and for the production of a broader range of organic compounds in two-liquid-phase bioreactor setups (11). m-Nitrotoluene was not oxidized in P. putida strains DOT-T1E and PpS81, yet the synthesis of oxidative enzymes involved in the mineralization of m-nitrotoluene via m-nitrobenzyl alcohol, m-nitrobenzaldehyde, and mnitrobenzoic acid has been reported for P. putida strain OU83 upon induction with m-nitrotoluene (1,50). Interestingly, mtoluidine accumulated as the main product, apparently without significant inhibition of the m-nitrotoluene hydroxylation.…”

Section: Discussionmentioning

confidence: 99%

“…Their electrophilic character makes them susceptible to reduction by all kinds of microbial systems (41). Numerous bacterial strains, such as those of Pseudomonas species (1,43) and E. coli (13), provide enzymes that are able to transform nitro groups of aromatic compounds under aerobic conditions. This indicates that biocatalysis of nitroaromatics might be complicated by influences of the enzymatic background activity of the host strain (52).…”

mentioning

confidence: 99%

Suitability of RecombinantEscherichia coliandPseudomonas putidaStrains for Selective Biotransformation ofm-Nitrotoluene by Xylene Monooxygenase

Meyer

Schmid

2005

Appl Environ Microbiol

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Escherichia coli JM101(pSPZ3), containing xylene monooxygenase (XMO) from Pseudomonas putida mt-2, catalyzes specific oxidations and reductions of m-nitrotoluene and derivatives thereof. In addition to reactions catalyzed by XMO, we focused on biotransformations by native enzymes of the E. coli host and their effect on overall biocatalyst performance. While m-nitrotoluene was consecutively oxygenated to m-nitrobenzyl alcohol, m-nitrobenzaldehyde, and m-nitrobenzoic acid by XMO, the oxidation was counteracted by an alcohol dehydrogenase(s) from the E. coli host, which reduced m-nitrobenzaldehyde to m-nitrobenzyl alcohol. Furthermore, the enzymatic background of the host reduced the nitro groups of the reactants resulting in the formation of aromatic amines, which were shown to effectively inhibit XMO in a reversible fashion. Host-intrinsic oxidoreductases and their reaction products had a major effect on the activity of XMO during biocatalysis of m-nitrotoluene. P. putida DOT-T1E and P. putida PpS81 were compared to E. coli JM101 as alternative hosts for XMO. These promising strains contained an additional dehydrogenase that oxidized m-nitrobenzaldehyde to the corresponding acid but catalyzed the formation of XMO-inhibiting aromatic amines at a significantly lower level than E. coli JM101.Microbial enzymes are useful catalysts for the degradation of organic pollutants in bioremediation but also for the synthesis of added-value products in biocatalytic applications. Various large-scale processes based on bacterial enzymes have been established (17,26,30,47), which illustrate the increasing impact of biocatalysis in the chemical industry (45). Heterologous gene expression has developed to a standard technology for increasing and controlling enzyme activities in bioprocesses. It allows catalysis of a variety of reactions in a limited number of bacterial strains used as recombinant hosts. The focus on a few suitable hosts is emphasized, e.g., by the PlugBug concept (DSM, Heerlen, The Netherlands). Of these strains, Escherichia coli strains are easily accessible for genetic and biochemical engineering and provide high metabolic activity for cofactor regeneration. Their use as recombinant hosts is especially favorable in cofactor-dependent oxygenase-based processes (7) for the conversion of various aromatic hydrocarbons to industrially relevant products (5, 38, 54). E. coli JM101(pSPZ3) (39) contains xylene monooxygenase (XMO) from Pseudomonas putida mt-2 and oxidizes the methyl groups of a variety of toluene and xylene derivatives to the corresponding alcohols, aldehydes, and acids (8,12,55).Nitroaromatics are widely used in large amounts as synthetic intermediates, dyes, pesticides, pharmaceuticals, and explosives (21, 46). Their electrophilic character makes them susceptible to reduction by all kinds of microbial systems (41). Numerous bacterial strains, such as those of Pseudomonas species (1, 43) and E. coli (13), provide enzymes that are able to transform nitro groups of aromatic compounds under aerobic condition...

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A novel pathway for the biodegradation of 3-nitrotoluene in Pseudomonas putida

Cited by 20 publications

References 25 publications

A New 4-Nitrotoluene Degradation Pathway in a Mycobacterium Strain

A New 4-Nitrotoluene Degradation Pathway in a Mycobacterium Strain

Evolution of efficient pathways for degradation of anthropogenic chemicals

Suitability of RecombinantEscherichia coliandPseudomonas putidaStrains for Selective Biotransformation ofm-Nitrotoluene by Xylene Monooxygenase

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