Influence of the methyl group in isoprene epoxides on reactivity compared to butadiene epoxides: Biological significance

Golding, Bernard T.; Abelairas-Edesa, Manuel; Tilbury, Rowena D; Wilson, Joanne P; Zhang, Daping; Henderson, Alex; Bleasdale, Christine; Clegg, William; Watson, William P.

doi:10.1016/j.cbi.2022.109949

Cited by 3 publications

(5 citation statements)

References 71 publications

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“…The relative transcription of the iso cluster during induction with epoxyisoprene decreased from 22.5% after 2 h to 0.1% after 4 h (Figure 2 ). The decrease in gene induction was likely to be caused by the loss of epoxyisoprene due to hydrolysis in water to the corresponding diol (Golding et al, 2022 ), rather than metabolism of epoxyisoprene to HGMB by the isoprene metabolic pathway. The abundances of Iso proteins at Timepoint 0 (0 h) accounted for 0.00001%–0.005% of the total proteome, compared 0.005%–3.32% of the total proteome after 30 h of growth on isoprene (Supplementary Data sheet S2 , L4501‐4514), making it unlikely that IsoI was present at sufficient abundance to catalyse the complete conversion of epoxyisoprene to HGMB within the initial 2–4 h period.…”

Section: Resultsmentioning

confidence: 99%

‘Omics‐guided prediction of the pathway for metabolism of isoprene by Variovorax sp. WS11

Dawson

Rix

Crombie

et al. 2022

Environmental Microbiology

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Bacteria that inhabit soils and the leaves of trees partially mitigate the release of the abundant volatile organic compound, isoprene (2-methyl-1,-3-butadiene). While the initial steps of isoprene metabolism were identified in Rhodococcus sp. AD45 two decades ago, the isoprene metabolic pathway still remains largely undefined. Limited understanding of the functions of isoG, isoJ and aldH and uncertainty in the route of isoprene-derived carbon into central metabolism have hindered our understanding of isoprene metabolism. These previously uncharacterised iso genes are essential in Variovorax sp. WS11, determined by targeted mutagenesis. Using combined 'omics-based approaches, we propose the complete isoprene metabolic pathway. Isoprene is converted to propionyl-CoA, which is assimilated by the chromosomally encoded methylmalonyl-CoA pathway, requiring biotin and vitamin B12, with the plasmid-encoded methylcitrate pathway potentially providing robustness against limitations in these vitamins. Key components of this pathway were induced by both isoprene and its initial oxidation product, epoxyisoprene, the principal inducer of isoprene metabolism in both Variovorax sp. WS11 and Rhodococcus sp. AD45. Analysis of the genomes of distinct isoprene-degrading bacteria indicated that all of the genetic components of the methylcitrate and methylmalonyl-CoA pathways are not always present in isoprene degraders, although incorporation of isoprene-derived carbon via propionyl-CoA and acetyl-CoA is universally indicated.

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Section: Resultsmentioning

confidence: 99%

‘Omics‐guided prediction of the pathway for metabolism of isoprene by Variovorax sp. WS11

Dawson

Rix

Crombie

et al. 2022

Environmental Microbiology

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“…We did not examine the structure of the reaction products because it is well known that the hydrolysis of one epoxide ring of DEB produces 3,4‐epoxybutane‐1,2‐diol that further hydrolyzes into threitol or erythritol 21,33 . Also, the molecular mechanisms of the three types of the DEB hydrolysis can be envisaged basing on the literature data 31,32,34–36 . Briefly, the acid hydrolysis of DEB begins with the protonation of the epoxy ring oxygen which makes it a better leaving group and affords a catalytic effect.…”

Section: Discussionmentioning

confidence: 99%

“…Which of these two mechanisms is preferred in case of the acid‐catalyzed hydrolysis of DEB remains an open question. The base‐catalyzed hydrolysis of DEB most likely involves a direct attack of the strong nucleophile OH − according to the pure S N 2 mechanism, with the primary carbon of the epoxide ring being a preferred target 31,34,35 . The neutral (pH‐independent) hydrolysis is also considered to follow the pure S N 2 mechanism.…”

Section: Discussionmentioning

confidence: 99%

“…21,33 Also, the molecular mechanisms of the three types of the DEB hydrolysis can be envisaged basing on the literature data. 31,32,[34][35][36] Briefly, the acid hydrolysis of DEB begins with the protonation of the epoxy ring oxygen which makes it a better leaving group and affords a catalytic effect. Then a water molecule (weak nucleophile) attacks the less hindered (primary) or more hindered (secondary) carbon atom from the opposite side to the leaving group, in the pure or borderline bimolecular nucleophilic substitution (S N 2), respectively.…”

Section: Discussionmentioning

confidence: 99%

“…The base-catalyzed hydrolysis of DEB most likely involves a direct attack of the strong nucleophile OH − according to the pure S N 2 mechanism, with the primary carbon of the epoxide ring being a preferred target. 31,34,35 The neutral (pH-independent) hydrolysis is also considered to follow the pure S N 2 mechanism. However, it lacks a strong nucleophile's attack as well as the ring's oxygen protonation, therefore proceeds much slower that the acid-and base-catalyzed reactions.…”

Section: Discussionmentioning

confidence: 99%

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Nonenzymatic hydrolysis of 1,2:3,4‐diepoxybutane: A kinetic study including pH, temperature, and ion effects

Romański,

Mikołajewski,

Główka

2023

Int J of Chemical Kinetics

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Abstract1,3‐Butadiene is a carcinogenic and mutagenic air pollutant metabolized to butane epoxides, among which 1,2:3,4‐diepoxybutane (DEB) exhibits the highest genotoxicity. DEB is also formed by 1,3‐butadiene oxidation in the air, producing a direct environmental and occupational exposure. In this paper, we studied the kinetics of the nonenzymatic hydrolysis of DEB at a wide range of pH and temperature, including the catalytic effect of ionic species. The compound degradation involved a general and specific acid‐base catalysis of the epoxide ring hydrolysis. DEB had the greatest stability at pH 5–9, when the rates of acid‐catalyzed and base‐catalyzed hydrolysis are negligible and the neutral hydrolysis predominates. The capability of the buffer anions to accelerate the DEB decay increased in the order H2PO4− < HCO3− < CH3COO− < HPO42− < and CO32−. The Arrhenius equation well described the influence of temperature on the acid‐catalyzed, base‐catalyzed, and neutral hydrolysis rate constants. According to the obtained hydrolysis model coupled with the found thermodynamic parameters, the half‐life of DEB in natural fresh waters spans from 2 days at 30°C to 31 days at 0°C, but in the laboratory waste adjusted to pH 1or 13, the half‐life shortens to 2–3 h at 20°C. Therefore, the results of the paper help to assess the risk of exposure to the genotoxic action of DEB.

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The effect of vitamin B12 on DNA adduction by styrene oxide, a genotoxic xenobiotic

Watson

Munter

Golding

2023

Chemico-Biological Interactions

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Influence of the methyl group in isoprene epoxides on reactivity compared to butadiene epoxides: Biological significance

Cited by 3 publications

References 71 publications

‘Omics‐guided prediction of the pathway for metabolism of isoprene by Variovorax sp. WS11

‘Omics‐guided prediction of the pathway for metabolism of isoprene by Variovorax sp. WS11

Nonenzymatic hydrolysis of 1,2:3,4‐diepoxybutane: A kinetic study including pH, temperature, and ion effects

The effect of vitamin B12 on DNA adduction by styrene oxide, a genotoxic xenobiotic

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