Stereochemical Consequences of Vinylpyruvate Hydratase-Catalyzed Reactions

Johnson, William H.; Stack, Tyler; Taylor, Stephanie M.; Burks, Elizabeth A.; Whitman, Christian P.

doi:10.1021/acs.biochem.6b00552

Cited by 2 publications

(23 citation statements)

References 38 publications

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“…The 5-bromo- and 5-fluoro-2-hydroxymuconates ( 3c and 3d ) were successfully synthesized following the protocol used elsewhere to generate 5-chloro-2-hydroxymuconate ( 3b ) [ 11 ]. These reactions combine the ethyl 2-halocrotonate with diethyl oxalate followed by alkaline hydrolysis and acidification.…”

Section: Resultsmentioning

confidence: 99%

“…Subsequently, the 4 Z -isomers of 5-bromo- and 5-fluoro-2-hydroxy-2,4-pentadienoates ( 5c and 5d ) were synthesized enzymatically (following the protocol for the 5-chloro derivative). The enzymatic synthesis relies on the actions of the 4-OT and 4-OD/E106QVPH (both from P. putida mt-2), which carry out ketonization and decarboxylation, respectively, of 3c and 3d [ 11 ]. (The 4-OD/E106QVPH retains full decarboxylase activity, but has very little hydratase activity [ 10 ].)…”

Section: Resultsmentioning

confidence: 99%

“…The Lc 4-OT shows high similarity (78% identity and 87% similarity) with the one found in Comamonas sp. strain CNB-1, which is not available [ 11 ]. The Lc 4-OT is more distantly related to the Pp 4-OT (45% identity and 71% similarity).…”

Section: Resultsmentioning

confidence: 99%

“…Ketonization of 3a to 2-oxo-3-hexenedioate ( 4a ) is catalyzed by 4-oxalocrotonate tautomerase (4-OT) [ 8 ]. Decarboxylation of 4a by the metal-dependent 4-oxalocrotonate decarboxylase (4-OD) generates 2-hydroxy-2,4-pentadienoate ( 5a ) [ 9 – 11 ]. 4-OD functions in a complex with the next enzyme in the pathway, a metal-dependent vinylpyruvate hydratase (VPH) [ 7 ].…”

Section: Introductionmentioning

confidence: 99%

“…4-OD functions in a complex with the next enzyme in the pathway, a metal-dependent vinylpyruvate hydratase (VPH) [ 7 ]. VPH catalyzes the addition of water to the C-4 position of 5a to produce ( S )-2-keto-4-hydroxypentanoate ( 6a ) [ 9 – 11 ]. A retro-aldol cleavage of 6a by pyruvate aldolase yields pyruvate and acetaldehyde ( 7a ).…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and enzymatic ketonization of the 5-(halo)-2-hydroxymuconates and 5-(halo)-2-hydroxy-2,4-pentadienoates

Stack¹,

Johnson²,

Whitman³

2017

Beilstein J. Org. Chem.

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5-Halo-2-hydroxymuconates and 5-halo-2-hydroxy-2,4-pentadienoates are stable dienols that are proposed intermediates in bacterial meta-fission pathways for the degradation of halogenated aromatic compounds. The presence of the halogen raises questions about how the bulk and/or electronegativity of these substrates would affect enzyme catalysis or whether some pathway enzymes have evolved to accommodate it. To address these questions, 5-halo-2-hydroxymuconates and 5-halo-2-hydroxy-2,4-pentadienoates (5-halo = Cl, Br, F) were synthesized and a preliminary analysis of their enzymatic properties carried out. In aqueous buffer, 5-halo-2-hydroxy-2,4-pentadienoates rapidly equilibrate with the β,γ-unsaturated ketones. For the 5-chloro and 5-bromo derivatives, a slower conversion to the α,β-isomers follows. There is no detectable formation of the α,β-isomer for the 5-fluoro derivative. Kinetic parameters were also obtained for both sets of compounds in the presence of 4-oxalocrotonate tautomerase (4-OT) from Pseudomonas putida mt-2 and Leptothrix cholodnii SP-6. For 5-halo-2-hydroxymuconates, there are no major differences in the kinetic parameters for the two enzymes (following the formation of the β,γ-unsaturated ketones). In contrast, the L. cholodnii SP-6 4-OT is ≈10-fold less efficient than the P. putida mt-2 4-OT in the formation of the β,γ-unsaturated ketones and the α,β-isomers from the 5-halo-2-hydroxy-2,4-pentadienoates. The implications of these findings are discussed. The availability of these compounds will facilitate future studies of the haloaromatic catabolic pathways.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis and enzymatic ketonization of the 5-(halo)-2-hydroxymuconates and 5-(halo)-2-hydroxy-2,4-pentadienoates

Stack¹,

Johnson²,

Whitman³

2017

Beilstein J. Org. Chem.

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Inactivation of 4-Oxalocrotonate Tautomerase by 5-Halo-2-hydroxy-2,4-pentadienoates

Stack

Johnson

et al. 2018

Biochemistry

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5-Halo-2-hydroxy-2,4-pentadienoates (5-halo-HPDs) are reportedly generated in the bacterial catabolism of halogenated aromatic hydrocarbons by the meta-fission pathway. The 5-halo-HPDs, where the halogen can be bromide, chloride, or fluoride, result in the irreversible inactivation of 4-oxalocrotonate tautomerase (4-OT), which precedes the enzyme that generates them. The loss of activity is due to the covalent modification of the nucleophilic amino-terminal proline. Mass spectral and crystallographic analysis of the modified enzymes indicates that inactivation of 4-OT by 5-chloro- and 5-bromo-2-hydroxy-2,4-pentadienoate follows a mechanism different from that for the inactivation of 4-OT by 5-fluoro-2-hydroxy-2,4-pentadienoate. The 5-chloro and 5-bromo derivatives undergo 4-OT-catalyzed tautomerization to their respective α,β-unsaturated ketones followed by attack at C5 (by the prolyl nitrogen) with concomitant loss of the halide. For the 5-fluoro species, the presence of a small amount of the α,β-unsaturated ketone could result in a Michael addition of the prolyl nitrogen to C4 followed by protonation at C3. The fluoride is not eliminated. These observations suggest that the inactivation of 4-OT by a downstream metabolite could hamper the efficacy of the pathway, which is the first time that such a bottleneck has been reported for the meta-fission pathway.

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Stereochemical Consequences of Vinylpyruvate Hydratase-Catalyzed Reactions

Cited by 2 publications

References 38 publications

Synthesis and enzymatic ketonization of the 5-(halo)-2-hydroxymuconates and 5-(halo)-2-hydroxy-2,4-pentadienoates

Synthesis and enzymatic ketonization of the 5-(halo)-2-hydroxymuconates and 5-(halo)-2-hydroxy-2,4-pentadienoates

Inactivation of 4-Oxalocrotonate Tautomerase by 5-Halo-2-hydroxy-2,4-pentadienoates

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