Coenzyme A-dependent Aerobic Metabolism of Benzoate via Epoxide Formation

Rather, Liv J.; Knapp, Bettina L.; Haehnel, Wolfgang; Fuchs, Georg

doi:10.1074/jbc.m110.124156

Cited by 49 publications

(59 citation statements)

References 47 publications

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“…In most BoxB ox structures, one bridging hydroxyl group is replaced by a ligand from the crystallization solution. According to EPR data, 4 the reaction cycle is initiated by reducing BoxB with BoxA/NADPH to a mixedvalent Fe1 II Fe2 III state, which is in agreement with theoretical studies on methane monooxygenase (40). In parallel, one or both bridging hydroxo groups are released as H 2 O.…”

Section: Resultssupporting

confidence: 67%

“…EPR spectroscopic measurements also using the physiological NADPH/BoxA system for reduction resulted in a semireduced Fe II Fe III center. 4 In vitro the fully reduced Fe II Fe II center was only achieved with the stronger reducing agent dithionite in the presence of methyl viologen. 4 Because of the deviating conditions concerning solution composition, time, and radiation used for x-ray and EPR studies, we cannot specify whether the diiron center in the crystal is present in the semireduced Fe II Fe III or the completely reduced Fe II Fe II state.…”

Section: Resultsmentioning

confidence: 99%

“…The key enzyme is BoxB. This 55-kDa monomeric protein catalyzes the transformation of benzoyl-CoA and oxygen with two electrons and two protons to the non-aromatic 2,3-epoxybenzoyl-CoA and water (4). BoxB is found with a sequence identity higher than 53% mainly in ␣-and ␤-proteobacteria.…”

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confidence: 99%

“…1). According to genome analysis, the pathway is present in 5% of all bacteria (4). Moreover, this strategy not only applies to the metabolism of benzoate but also of phenylacetate (5).…”

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confidence: 99%

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Structure and Mechanism of the Diiron Benzoyl-Coenzyme A Epoxidase BoxB

Rather

Weinert

Demmer

et al. 2011

Journal of Biological Chemistry

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The coenzyme A (CoA)-dependent aerobic benzoate metabolic pathway uses an unprecedented chemical strategy to overcome the high aromatic resonance energy by forming the nonaromatic 2,3-epoxybenzoyl-CoA. The crucial dearomatizing reaction is catalyzed by three enzymes, BoxABC, where BoxA is an NADPH-dependent reductase, BoxB is a benzoyl-CoA 2,3-epoxidase, and BoxC is an epoxide ring hydrolase. We characterized the key enzyme BoxB from Azoarcus evansii by structural and Mössbauer spectroscopic methods as a new member of class I diiron enzymes. Several family members were structurally studied with respect to the diiron center architecture, but no structure of an intact diiron enzyme with its natural substrate has been reported. X-ray structures between 1.9 and 2.5 Å resolution were determined for BoxB in the diferric state and with bound substrate benzoyl-CoA in the reduced state. The substrate-bound reduced state is distinguished from the diferric state by increased iron-ligand distances and the absence of directly bridging groups between them. The position of benzoylCoA inside a 20 Å long channel and the position of the phenyl ring relative to the diiron center are accurately defined. The C2 and C3 atoms of the phenyl ring are closer to one of the irons. Therefore, one oxygen of activated O 2 must be ligated predominantly to this proximate iron to be in a geometrically suitable position to attack the phenyl ring. Consistent with the observed iron/phenyl geometry, BoxB stereoselectively should form the 2S,3R-epoxide. We postulate a reaction cycle that allows a charge delocalization because of the phenyl ring and the electron-withdrawing CoA thioester.The metabolism of aromatic compounds has attracted broad attention due to its importance in the biogeochemical carbon cycle (includes 10 -20% of the biomass) and because of the chemistry necessary to overcome the high resonance energy of the conjugated cyclic ring. A central intermediate of the aromatic metabolism is benzoate, which can be degraded by microorganisms using three different strategies. The first strategy in the presence of oxygen uses mono-and dioxygenases to hydroxylate benzoate to catechol or protocatechuate. Central ring-cleaving dioxygenases with mononuclear iron centers subsequently cleave the aromatic ring either between the two hydroxyl groups (ortho cleavage, ␤-ketoadipate pathway) or next to one of the hydroxyl groups (meta cleavage) (1). The second strategy under anoxic conditions involves benzoylCoA, which is reduced by two electrons to a non-aromatic cyclic diene followed by hydrolytic ring opening. Benzoyl-CoA reduction is accomplished by two completely different enzyme systems that may catalyze a Birch-like reduction (2).The third, semi-aerobic strategy to metabolize benzoate shares characteristic features of both of these options (3). Oxygen is still required for attacking the ring, as in the aerobic metabolism, whereas all metabolites are activated to CoA thioesters and ring cleavage is performed hydrolytically, as in the anaerobic pathwa...

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Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

“…1). According to genome analysis, the pathway is present in 5% of all bacteria (4). Moreover, this strategy not only applies to the metabolism of benzoate but also of phenylacetate (5).…”

mentioning

confidence: 99%

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Structure and Mechanism of the Diiron Benzoyl-Coenzyme A Epoxidase BoxB

Rather

Weinert

Demmer

et al. 2011

Journal of Biological Chemistry

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“…The 3,4-dehydroadipyl-CoA semialdehyde formed becomes converted to succinyl-CoA and acetyl-CoA by a ␤-oxidation-like metabolism (box lower pathway) (Fig. 1A) (8,(13)(14)(15)(16)(17)(18)(19)(20)(21)(22).…”

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confidence: 99%

Bacterial Degradation of Benzoate

Valderrama

Durante‐Rodríguez

Blázquez

et al. 2012

Journal of Biological Chemistry

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Benzoyl‐ CoA Epoxidase of Azoarcus evansii

Weinert

Rather‐Adler

Bill³

et al. 2004

Encyclopedia of Inorganic and Bioinorganic Chemistry

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Mineralization of aromatic compounds—present in large amounts in the biosphere—is a challenging chemical process. Nature developed several sophisticated degradation strategies, one of them being the benzoate‐degrading CoA‐linked Box pathway that is present in 5% of all sequenced bacterial genomes. The central dearomatization and cleavage reaction is accomplished by the BoxABC multicomponent system; BoxA is a reductase, BoxB an epoxidase using a single O 2 molecule, and BoxC a stimulator for the BoxB reaction and a hydrolase for subsequent ring cleavage. BoxB is a member of the important diiron carboxylate protein family characterized by a catalytic diiron center embedded in a central four‐helix bundle. Benzoyl‐CoA is located inside a 20 Å long channel of BoxB. The position of its phenyl ring relative to the diiron center is accurately defined in the X‐ray structure and allowed valuable insight into O 2 binding and activation, epoxidation, and the stereoselectivity of the reaction. Kinetic‐ and electron paramagnetic resonance (EPR)‐spectroscopic investigations provided information about the reaction dynamics and reaction intermediates. On the basis of the total data available, a detailed enzymatic mechanism is proposed.

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Coenzyme A-dependent Aerobic Metabolism of Benzoate via Epoxide Formation

Cited by 49 publications

References 47 publications

Structure and Mechanism of the Diiron Benzoyl-Coenzyme A Epoxidase BoxB

Structure and Mechanism of the Diiron Benzoyl-Coenzyme A Epoxidase BoxB

Bacterial Degradation of Benzoate

Benzoyl‐ CoA Epoxidase of Azoarcus evansii

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