A Previously Unrecognized Step in Pentachlorophenol Degradation in
            <i>Sphingobium chlorophenolicum</i>
            Is Catalyzed by Tetrachlorobenzoquinone Reductase (PcpD)

Dai, MingHua; Rogers, Julie Bull; Warner, Joseph R.; Copley, Shelley D.

doi:10.1128/jb.185.1.302-310.2003

Cited by 70 publications

(97 citation statements)

References 29 publications

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“…Methyl-5-nitrocatechol 5-monooxygenase of Burkholderia strain DNT4 converts 4-methyl-5-nitrocatechol to relatively stable 2-hydroxy-5-methylquinone with nitrite elimination, and the bacterium has a quinone reductase to reduce the quinone to 2-hydroxy-5-methylquinol (22). Sphingomobium chlorophenolicum pentachlorophenol 4-monooxygenase converts pentachlorophenol to tetrachloroquinol with the consumption of 1 O 2 and 2 NADH (32); however, the enzyme really produces tetrachloroquinone, which is not stable and is immediately reduced to tetrachloroquinol by chemical reaction or enzymatic reactions at the expense of NADH (21). A direct comparison of normal oxidation and dechlorinating oxidation by TftD of B. cepacia AC1100 is shown in Fig.…”

Section: Fig 4 the Mass Spectra Of Acetylated 6-chlorohydroxyquinolmentioning

confidence: 99%

“…NADH, ascorbate; Refs. 20,21) or by quinone reductases (20,21). It is likely the produced 2,6-dichloroquinone has two fates: the minor one is to be reduced to 2,6-dichloroquinol by reducing agents in the reaction mixture, and the major one is to be hydrolyzed by TcpA to 6-chlorohydroxyquinone, which is chemically reduced to 6-chlorohydroxyquinol.…”

Section: Fig 4 the Mass Spectra Of Acetylated 6-chlorohydroxyquinolmentioning

confidence: 99%

“…NADH and ascorbate can chemically reduce the latter to 6-chlorohydroxyquinol in the reaction mixture ( Fig. 1), but this may occur enzymatically inside the cell (20,21).…”

mentioning

confidence: 99%

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A Monooxygenase Catalyzes Sequential Dechlorinations of 2,4,6-Trichlorophenol by Oxidative and Hydrolytic Reactions

Xun

Webster

2004

Journal of Biological Chemistry

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Ralstonia eutropha JMP134 2,4,6-trichlorophenol (2,4,6-TCP) 4-monooxygenase catalyzes sequential dechlorinations of 2,4,6-TCP to 6-chlorohydroxyquinol. Although 2,6-dichlorohydroxyquinol is a logical metabolic intermediate, the enzyme hardly uses it as a substrate, implying it may not be a true intermediate. Evidence is provided to support the proposition that the monooxygenase oxidized 2,4,6-TCP to 2,6-dichloroquinone that remained with the enzyme and got hydrolyzed to 2-chlorohydroxyquinone, which was chemically reduced by ascorbate and NADH to 6-chlorohydroxyquinol. When the monooxygenase oxidized 2,6-dichlorophenol, the product was 2,6-dichloroquinol, which was not further converted to 6-chlorohydroxyquinol, implying that the enzyme only converts 2,6-dichloroquinone to 6-chlorohydroxyquinol. Stoichiometric analysis indicated the consumption of one O 2 molecule per 2,4,6-TCP converted to 6-chlorohydroxyquinol, ruling out the possibility of two oxidative reactions. Experiments with 18 Olabeling gave direct evidence for the incorporation of oxygen from both O 2 and H 2 O into the produced 6-chlorohydroxyquinol. A monooxygenase that catalyzes hydroxylation by both oxidative and hydrolytic reactions has not been reported to date. The ability of the enzyme to perform two types of reactions is not due to the presence of a second functional domain but rather is due to catalytic promiscuity, as a homologous monooxygenase converts 2,4,6-TCP to only 2,6-dichloroquinol. Employing both conventional catalysis and catalytic promiscuity of a single enzyme in two consecutive steps of a metabolic pathway has been unknown previously.

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Section: Fig 4 the Mass Spectra Of Acetylated 6-chlorohydroxyquinolmentioning

confidence: 99%

Section: Fig 4 the Mass Spectra Of Acetylated 6-chlorohydroxyquinolmentioning

confidence: 99%

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A Monooxygenase Catalyzes Sequential Dechlorinations of 2,4,6-Trichlorophenol by Oxidative and Hydrolytic Reactions

Xun

Webster

2004

Journal of Biological Chemistry

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“…Like these microbes, S. chlorophenolicum contains a gene encoding a reductase (PcpD) immediately downstream of the gene encoding the hydroxylase (PcpB). We have previously shown that pcpD is essential for survival of S. chlorophenolicum at high concentrations of PCP but is not essential for survival at high concentrations of 2,3,5,6-tetrachlorophenol (TCP) (2). In this work, we have addressed the mechanism of that protection.…”

mentioning

confidence: 99%

“…2B). In addition, we have previously reported that incubation of PcpB with TCBQ causes loss of catalytic activity (2).…”

mentioning

confidence: 99%

Sequestration of a highly reactive intermediate in an evolving pathway for degradation of pentachlorophenol

Yadid

Rudolph

Hlouchová

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Microbes in contaminated environments often evolve new metabolic pathways for detoxification or degradation of pollutants. In some cases, intermediates in newly evolved pathways are more toxic than the initial compound. The initial step in the degradation of pentachlorophenol by Sphingobium chlorophenolicum generates a particularly reactive intermediate; tetrachlorobenzoquinone (TCBQ) is a potent alkylating agent that reacts with cellular thiols at a diffusion-controlled rate. TCBQ reductase (PcpD), an FMN-and NADH-dependent reductase, catalyzes the reduction of TCBQ to tetrachlorohydroquinone. In the presence of PcpD, TCBQ formed by pentachlorophenol hydroxylase (PcpB) is sequestered until it is reduced to the less toxic tetrachlorohydroquinone, protecting the bacterium from the toxic effects of TCBQ and maintaining flux through the pathway. The toxicity of TCBQ may have exerted selective pressure to maintain slow turnover of PcpB (0.02 s −1 ) so that a transient interaction between PcpB and PcpD can occur before TCBQ is released from the active site of PcpB.biodegradation | molecular evolution | channeling | quinone reductase

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Catabolic Plasmids

Schmidt¹,

Ahmetagic²,

Philip³

et al. 2011

Encyclopedia of Life Sciences

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Catabolic plasmids are large (80→1100 kb) linear or circular, accessory deoxyribonucleic acid elements present in the cytoplasm of bacteria from virtually every ecological niche on Earth. Many have a broad host range and can be transferred by cell‐to‐cell contact to a wide range of bacteria. The large catabolic gene clusters carried by these plasmids play a central role in the Earth's carbon cycle, enabling their hosts to degrade and recycle complex naturally occurring molecules such as lignin, the second most abundant plant biopolymer on Earth after cellulose. More recently catabolic gene clusters have evolved the ability to degrade and recycle most man made molecules, including the most toxic and the most recalcitrant environmental pollutants, providing a biological solution to environmental pollution. Catabolic genes have been used to construct novel strains of bacteria which produce biopharmaceuticals such as antibiotics and anticancer agents, biofuels such as ethanol, industrial dyes such as indigo and biodegradable plastics. The very first patent for a genetically modified organism was for the use of catabolic plasmids to degrade oil. Key Concepts: Catabolic plasmids are giant bacterial plasmids that encode vast arrays of catabolic gene clusters. They play a central and indispensible role in the Earth's carbon cycle. Catabolic plasmids are essential for the degradation and recycling of abundant, naturally occurring yet chemically complex plant materials such as lignin. In addition, there are catabolic plasmids, which enable bacteria to degrade and recycle the most complex, most toxic and the most polluting man‐made molecules including most carcinogens, teratogens and mutagens. Degradation and recycling of such complex molecules at room temperature and pressure, so called ‘green or eco‐friendly’ chemistry, requires many different enzymes encoded in large arrays of gene clusters. To accommodate these genes on catabolic plasmids they must be very large. Some are in excess of 1000 kb. Many catabolic plasmids are transferable from one bacterial cell to another by cell‐to‐cell contact. They have an extraordinarily broad host range being able to rapidly confer their catabolic activities on large populations of soil bacteria. Novel catabolic functions can be produced by rearranging existing pathway genes, combining genes from different pathways to form a new pathway and by fusing segments from a number of pre‐existing catabolic genes into a new catabolic gene. The genes encoded by catabolic plasmids have been harnessed by humans to produce antibiotics and anticancer drugs, to synthesise biofuels such as ethanol from lignin and to degrade and recycle man‐made environmental pollutants. The very first patent to be granted for a genetically modified organism was for catabolic plasmids that encoded the degradation of environmental oil spills.

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A Previously Unrecognized Step in Pentachlorophenol Degradation in Sphingobium chlorophenolicum Is Catalyzed by Tetrachlorobenzoquinone Reductase (PcpD)

Cited by 70 publications

References 29 publications

A Monooxygenase Catalyzes Sequential Dechlorinations of 2,4,6-Trichlorophenol by Oxidative and Hydrolytic Reactions

A Monooxygenase Catalyzes Sequential Dechlorinations of 2,4,6-Trichlorophenol by Oxidative and Hydrolytic Reactions

Sequestration of a highly reactive intermediate in an evolving pathway for degradation of pentachlorophenol

Catabolic Plasmids

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