Anaerobic carboxylation of phenol to benzoate: use of deuterated phenols revealed carboxylation exclusively in the C4-position

Gallert, Claudia; Knoll, Gertrud; Winter, Josef

doi:10.1007/bf00164712

Cited by 34 publications

(28 citation statements)

References 20 publications

(21 reference statements)

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“…In accordance with this proposal, the phenol-carboxylating enzyme system in a phenol-degrading defined mixed culture also catalyses an H/D exchange at C4 of phenol, the site to be carboxylated (Gallert et al, 1991). Dephosphorylation would drive the reaction forward and a firmly enzyme-bound phenolate anion appears to be a suitable nucleophilic acceptor to be carboxylated by CO, rather than bicarbonate.…”

Section: C6h-oh + X-po:--ch-o-po:-+ X-h (9)mentioning

confidence: 66%

“…Anaerobic degradation of phenol, aniline, o-cresol, hydroquinone and catechol by denitrifying and sulfate-reducing bacteria involves carboxylation of the aromatic ring (Bak and Widdel, 1986;Tschech and Fuchc, 1987;Roberts et al, 1990;Schnell et al, 1991 ;Rudolphi et al, 1991 ;Bisaillon et al, 1991 ;Gallert et al, 1991;Gorny and Schink, 1994a,b,c). In these cases a typical CO, dependence of substrate conversion can be observed in cell suspensions or extracts.…”

Section: Peripheral Metabolic Reactionsmentioning

confidence: 99%

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Anaerobic Metabolism of Aromatic Compounds

Heider

Fuchs

1997

European Journal of Biochemistry

285

214

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Aromatic compounds comprise a wide variety of low-molecular-mass natural compounds (amino acids, quinones, flavonoids, etc.) and biopolymers (lignin, melanin). They are almost exclusively degraded by microorganisms. Aerobic aromatic metabolism is characterised by the extensive use of molecular oxygen. Monoxygenases and dioxygenases are essential for the hydroxylation and cleavage of aromatic ring structures. Accordingly, the characteristic central intermediates of the aerobic pathways (e.g. catechol) are readily attacked oxidatively. Anaerobic aromatic catabolism requires, of necessity, a quite different strategy. The basic features of this metabolism have emerged from studies on bacteria that degrade soluble aromatic substrates to CO, in the complete absence of molecular oxygen.Essential to anaerobic aromatic metabolism is the replacement of all the oxygen-dependent steps by an alternative set of novel reactions and the formation of different central intermediates (e.g. benzoylCoA) for breaking the aromaticity and cleaving the ring; notably, in anaerobic pathways, the aromatic ring is reduced rather than oxidised. The two-electron reduction of benzoyl-CoA to a cyclic diene requires the cleavage of two molecules of ATP to ADP and P, and is catalysed by benzoyl-CoA reductase. After nitrogenase, this is the second enzyme known which overcomes the high activation energy required for reduction of a chemically stable bond by coupling electron transfer to the hydrolysis of ATP. The alicyclic product cyclohex-I ,5-diene-l-carboxyl-CoA is oxidised to acetyl-CoA via a modified P-oxidation pathway ; the ring structure is opened hydrolytically. Some phenolic compounds are anaerobically transformed to resorcinol (1,3-dihydroxybenzene) or phloroglucinol (1,3,5-trihydroxybenzene). These intermediates are also first reduced and then as alicyclic products oxidised to acetyl-CoA.This review gives an outline of the anaerobic pathways which allow bacteria to utilize aromatics even in the absence of oxygen. We focus on previously unknown reactions and on the enzymes characteristic for such novel metabolism.Keywords ; aromatic metabolism ; benzoyl-CoA ; anaerobic bacteria ; aromatic-ring reduction ; phloroglucinol; resorcinol.This review deals with the art of degrading aromatic compounds to CO, in the complete absence of molecular oxygen. This ability allows bacteria to make use of natural compounds of this widespread class as substrates for growth under anoxic conditions. In nature, anoxic conditions are created when oxygen consumption exceeds its supply. This situation prevails in many environments, e.g. in the intestinal tract of animals and man, in the sediments of all natural bodies of water, in ground water and in part in soil. Aromatic compounds are produced or transformed by all organisms, plants being the most prolific producers. There are numerous low-molecular-mass aromatic compounds includ-

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Section: C6h-oh + X-po:--ch-o-po:-+ X-h (9)mentioning

confidence: 66%

Section: Peripheral Metabolic Reactionsmentioning

confidence: 99%

Anaerobic Metabolism of Aromatic Compounds

Heider

Fuchs

1997

European Journal of Biochemistry

285

214

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“…Consortia of fermenting bacteria convert phenol to benzoate (41) and decarboxylate 4-hydroxybenzoate to phenol (66). They also catalyze an isotope exchange between D 2 O and the proton at C-4 (24). Aerobic ortho carboxylation of aniline to 2-aminobenzoic acid has been reported for Rhodococcus erythropolis (2).…”

Section: Discussionmentioning

confidence: 99%

Phenylphosphate Carboxylase: a New C-C Lyase Involved in Anaerobic Phenol Metabolism in Thauera aromatica

2004

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The anaerobic metabolism of phenol in the beta-proteobacterium Thauera aromatica proceeds via carboxylation to 4-hydroxybenzoate and is initiated by the ATP-dependent conversion of phenol to phenylphosphate. The subsequent para carboxylation of phenylphosphate to 4-hydroxybenzoate is catalyzed by phenylphosphate carboxylase, which was purified and studied. This enzyme consists of four proteins with molecular masses of 54, 53, 18, and 10 kDa, whose genes are located adjacent to each other in the phenol gene cluster which codes for phenol-induced proteins. Three of the subunits (54, 53, and 10 kDa) were sufficient to catalyze the exchange of 14 CO 2 and the carboxyl group of 4-hydroxybenzoate but not phenylphosphate carboxylation. Phenylphosphate carboxylation was restored when the 18-kDa subunit was added. The following reaction model is proposed. The 14 CO 2 exchange reaction catalyzed by the three subunits of the core enzyme requires the fully reversible release of CO 2 from 4-hydroxybenzoate with formation of a tightly enzyme-bound phenolate intermediate. Carboxylation of phenylphosphate requires in addition the 18-kDa subunit, which is thought to form the same enzyme-bound energized phenolate intermediate from phenylphosphate with virtually irreversible release of phosphate. The 54-and 53-kDa subunits show similarity to UbiD of Escherichia coli, which catalyzes the decarboxylation of a 4-hydroxybenzoate derivative in ubiquinone (ubi) biosynthesis. They also show similarity to components of various decarboxylases acting on aromatic carboxylic acids, such as 4-hydroxybenzoate or vanillate, whereas the 10-kDa subunit is unique. The 18-kDa subunit belongs to a hydratase/ phosphatase protein family. Phenylphosphate carboxylase is a member of a new family of carboxylases/ decarboxylases that act on phenolic compounds, use CO 2 as a substrate, do not contain biotin or thiamine diphosphate, require K ؉ and a divalent metal cation (Mg 2؉ or Mn 2؉ ) for activity, and are strongly inhibited by oxygen.The anaerobic metabolism of phenol has been studied to some extent in the beta-proteobacterium Thauera aromatica. The two initial steps of the pathway consist of the phosphorylation of phenol to phenylphosphate and the carboxylation of phenylphosphate to 4-hydroxybenzoate (36-38) (Fig. 1). Both enzyme activities are induced in cells grown anoxically on phenol and nitrate and not in cells grown on 4-hydroxybenzoate, the product of this process. 4-Hydroxybenzoate is also an intermediate in the metabolism of p-cresol (53)Further metabolism of 4-hydroxybenzoate proceeds via benzoyl coenzyme A (benzoyl-CoA) in two steps (Fig. 1). A specific CoA ligase forms 4-hydroxybenzoyl-CoA (7, 25), which is reductively dehydroxylated to benzoyl-CoA by a molybdoflavo-iron-sulfur protein, 4-hydroxybenzoyl-CoA reductase (13,15,26). The electron donor is a 2-[4Fe/4S] ferredoxin which is reduced by 2-oxoglutarate-ferredoxin oxidoreductase (21). Benzoyl-CoA is a common intermediate in the metabolism of many aromatic compounds. It is reductively d...

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“…Phenol-transforming consortia enriched from methanogenic environments metabolize phenol via 4-hydroxybenzoate (4-OHB) and benzoate (Bisaillon et al, 1991a(Bisaillon et al, , 1993Gallert et al, 1991;Sharak Genthner et al, 1990;. Most attempts to isolate the strain responsible for the transformation of phenol from these consortia have failed.…”

Section: D]-phenol 4-ohb Was Shown To Be An Intermediate In the Tranmentioning

confidence: 99%

Cryptanaerobacter phenolicus gen. nov., sp. nov., an anaerobe that transforms phenol into benzoate via 4-hydroxybenzoate

Juteau

Côté

Duckett

et al. 2005

International Journal of Systematic and Evolutionary Microbiology

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An anaerobic bacterium that transforms phenol and 4-hydroxybenzoate (4-OHB) into benzoate, strain LR7.2T, was isolated from a culture originating from a mixture of swamp water, sewage sludge, swine waste and soil. Cells of strain LR7.2T are Gram-positive short rods (1×2 μm) that are electron-dense when observed by electron microscopy. The optimum pH and temperature for growth and transformation activity of 4-OHB are 7·5–8·0 and 30–37 °C, respectively. The bacterium does not use sulphate, thiosulphate, nitrate, nitrite, FeCl3, fumarate or arsenate as an electron acceptor. It does not normally use sulphite, although stimulation of growth and 4-OHB transformation activity at a low concentration (up to 2 mM) has been reported previously under different culture conditions. The presence of 4-OHB or phenol is essential for growth; transformation of 4-OHB or phenol into benzoate is used to produce energy for growth. Using [6D]-phenol, 4-OHB was shown to be an intermediate in the transformation of phenol into benzoate. No spore was observed. The bacterium has a DNA G+C content of 51 mol% and its major membrane fatty acid is anteiso-C15 : 0. The 16S rRNA gene sequence of strain LR7.2T shows only 90 % similarity to its closest relative (Pelotomaculum thermopropionicum). From these results, a new taxon is proposed: Cryptanaerobacter phenolicus gen. nov., sp. nov. The type strain is LR7.2T (=ATCC BAA-820T=DSM 15808T).

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Anaerobic carboxylation of phenol to benzoate: use of deuterated phenols revealed carboxylation exclusively in the C4-position

Cited by 34 publications

References 20 publications

Anaerobic Metabolism of Aromatic Compounds

Anaerobic Metabolism of Aromatic Compounds

Phenylphosphate Carboxylase: a New C-C Lyase Involved in Anaerobic Phenol Metabolism in Thauera aromatica

Cryptanaerobacter phenolicus gen. nov., sp. nov., an anaerobe that transforms phenol into benzoate via 4-hydroxybenzoate

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