Dithiol- and NAD-dependent degradation of epoxyalkanes by Xanthobacter Py2

Weijers, C.A.G.M.; Jongejan, H.; Franssen, M.C.R.; Groot, Aede de; Bont, J.A.M. de

doi:10.1007/s002530050330

Cited by 14 publications

(34 citation statements)

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“…The effect of CO 2 on the in vitro degradation of propylene oxide and the production of acetone was examined to determine whether the proposed carboxylation reaction could be measured in vitro. Consistent with the results of Weijers et al (14), in the absence of CO 2 , acetone was formed as a stoichiometric product of propylene oxide degradation, and the time course of acetone formation correlated with the time course of propylene oxide consumption (Fig. 2).…”

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confidence: 79%

“…1A) has been observed in whole-cell suspensions (10) and cell extracts of Xanthobacter strain Py2 (14). However, these ketones are not further metabolized, suggesting that they are not the physiological products of epoxide conversions.…”

mentioning

confidence: 99%

“…Weijers and coworkers have recently demonstrated that the degradation of epoxides in cell extracts of Xanthobacter strain Py2 is dependent upon the addition of NAD ϩ and a dithiol such as DTT (14). Under these conditions, several epoxides were stoichiometrically isomerized to the corresponding ketones.…”

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Carboxylation of epoxides to beta-keto acids in cell extracts of Xanthobacter strain Py2

Allen

Ensign

1996

J Bacteriol

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A novel enzymatic reaction involved in the metabolism of aliphatic epoxides by Xanthobacter strain Py2 is described. Cell extracts catalyzed the CO 2 -dependent carboxylation of propylene oxide (epoxypropane) to form acetoacetate and ␤-hydroxybutyrate. The time courses of acetoacetate and ␤-hydroxybutyrate formation indicate that acetoacetate is the primary product of propylene oxide carboxylation and that ␤-hydroxybutyrate is a secondary product formed by the reduction of acetoacetate. Analogous C 5 carboxylation products were identified with 1,2-epoxybutane as the substrate. In the absence of CO 2 , propylene oxide and 1,2-epoxybutane were isomerized to form acetone and methyl ethyl ketone, respectively, as dead-end products. The carboxylation of short-chain epoxides to ␤-keto acids is proposed to serve as the physiological reaction for the metabolism of aliphatic epoxides in Xanthobacter strain Py2.Xanthobacter strain Py2 is one of several bacteria capable of aerobic growth with aliphatic alkenes as carbon and energy sources (4). The pathway of alkene metabolism involves an initial monooxygenase-catalyzed reaction producing epoxide intermediates (12), as shown for the substrate propylene and the product propylene oxide (epoxypropane) in the following equation:Aliphatic epoxides such as propylene oxide have toxic, mutagenic, and potential carcinogenic properties (2, 13), and their metabolism in bacteria and mammalian systems has been the focus of considerable research in recent years. The best-characterized epoxide-degrading enzymes are the detoxifying epoxide hydrolases of mammalian cells, which hydrate epoxides to dihydrodiols (11). The hydrolysis of epoxides to diols has also been described as a bacterial mechanism for the utilization of epoxides as carbon and energy sources (1, 6). Another mechanism has been described for styrene-degrading bacteria, which metabolize the styrene epoxidation product, styrene oxide, via an isomerization reaction which yields phenylacetaldehyde as an intermediate product (5,8).The isomerization of short-chain epoxides to ketones (Fig. 1A) has been observed in whole-cell suspensions (10) and cell extracts of Xanthobacter strain Py2 (14). However, these ketones are not further metabolized, suggesting that they are not the physiological products of epoxide conversions. Recently, we demonstrated that the isomerization of epoxides to ketones by whole-cell suspensions of Xanthobacter Py2 occurred only when CO 2 was excluded from the assay mixture (9). This observation was extended to demonstrate that the metabolism of propylene oxide proceeds by a CO 2 -dependent reaction which was proposed to produce acetoacetate, or a derivative thereof (9). This proposed carboxylation, shown in Fig. 1B, represents a new and novel strategy for epoxide conversion distinct from hydrolytic and isomerization mechanisms such as those described above.To date, no direct evidence for epoxide carboxylation has been provided through in vitro studies. In this study, the in vitro carboxylation of short-chain...

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confidence: 79%

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Carboxylation of epoxides to beta-keto acids in cell extracts of Xanthobacter strain Py2

Allen

Ensign

1996

J Bacteriol

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“…For the epoxide carboxylase, a dithiol (e.g., dithiothreitol) and NAD ϩ were required for activity in cell extracts, while the addition of ATP did not stimulate activity (1). In the absence of CO 2 , the epoxide carboxylase of Xanthobacter strain Py2 catalyzed the isomerization of propylene oxide to produce acetone as a dead-end product in a reaction that also required NAD ϩ and a dithiol (1,25). In contrast to these results, the acetone carboxylase activity described in the present paper required ATP for activity, while dithiothreitol and NAD ϩ had no affect on activity.…”

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confidence: 99%

“…For example, the carboxylation of propylene oxide (epoxypropane), an isomer of acetone, leads to the formation of acetoacetate, the same product proposed for acetone carboxylation (1). In the absence of CO 2 , the epoxide carboxylase catalyzes the isomerization of epoxides to the corresponding ketones (1,25). These ketone products are not further metabolized.…”

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Involvement of an ATP-dependent carboxylase in a CO2-dependent pathway of acetone metabolism by Xanthobacter strain Py2

et al. 1996

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The metabolism of acetone by the aerobic bacterium Xanthobacter strain Py2 was investigated. Cell suspensions of Xanthobacter strain Py2 grown with propylene or glucose as carbon sources were unable to metabolize acetone. The addition of acetone to cultures grown with propylene or glucose resulted in a time-dependent increase in acetone-degrading activity. The degradation of acetone by these cultures was prevented by the addition of rifampin and chloramphenicol, demonstrating that new protein synthesis was required for the induction of acetone-degrading activity. In vivo and in vitro studies of acetone-grown Xanthobacter strain Py2 revealed a CO 2 -dependent pathway of acetone metabolism for this bacterium. The depletion of CO 2 from cultures grown with acetone, but not glucose or n-propanol, prevented bacterial growth. The degradation of acetone by whole-cell suspensions of acetone-grown cells was stimulated by the addition of CO 2 and was prevented by the depletion of CO 2 . The degradation of acetone by acetone-grown cell suspensions supported the fixation of 14 CO 2 into acid-stable products, while the degradation of glucose or ␤-hydroxybutyrate did not. Cultures grown with acetone in a nitrogen-deficient medium supplemented with NaH 13 CO 3 specifically incorporated 13 C-label into the C-1 (major labeled position) and C-3 (minor labeled position) carbon atoms of the endogenous storage compound poly-␤-hydroxybutyrate. Cell extracts prepared from acetone-grown cells catalyzed the CO 2 -and ATP-dependent carboxylation of acetone to form acetoacetate as a stoichiometric product. ADP or AMP were incapable of supporting acetone carboxylation in cell extracts. The sustained carboxylation of acetone in cell extracts required the addition of an ATP-regenerating system consisting of phosphocreatine and creatine kinase, suggesting that the carboxylation of acetone is coupled to ATP hydrolysis. Together, these studies provide the first demonstration of a CO 2 -dependent pathway of acetone metabolism for a strictly aerobic bacterium and provide direct evidence for the involvement of an ATP-dependent carboxylase in bacterial acetone metabolism.A variety of aerobic and anaerobic bacteria are capable of growth by using acetone as a source of carbon and energy. For some aerobic bacteria, the metabolism of acetone has been proposed to proceed via an O 2 -and reductant-dependent hydroxylation reaction producing acetol-(1-hydroxyacetone) as the initial product (4,12,21,23). For anaerobic bacteria, the metabolism of acetone has been proposed to proceed via a CO 2 -dependent carboxylation reaction producing acetoacetate as the initial product as shown in the following equation (2,10,11,13,14,(16)(17)(18): CH 3 COCH 3 ϩ CO 2 3CH 3 COCH 2 COO Ϫ . The carboxylation of acetone is the reverse of acetoacetate decarboxylation, a terminal reaction catalyzed by acetoacetate decarboxylases in certain fermentative bacteria of the genus Clostridium (6, 26).Acetoacetate decarboxylation represents the thermodynamically favorable direction for...

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Utilisation of C₂–C₄ gaseous hydrocarbons and isoprene by microorganisms

Shennan¹

2005

J of Chemical Tech & Biotech

101

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Microorganisms able to grow on low molecular weight aliphatic hydrocarbon gases, i.e. the n-alkanes, ethane, propane and butane, and the terminal alkenes, ethylene, propylene and butylene, are not uncommon but mainly belong to certain taxonomic groups. These microbes are described in this review together with the pathways by which the hydrocarbons are assimilated. Microbial oxidation of the volatile alkadiene, isoprene, is also discussed. Avenues for possible commercial exploitation of these metabolic activities are also reviewed. Short-chain n-alkane-utilising organisms have been investigated as tools in petroleum exploration and for production of single cell protein. More recently microbes grown on gaseous hydrocarbons other than methane have been evaluated for use in biotechnological production of epoxides, synthesis of chiral epoxyalkanes and as catalysts in bioremediation systems.  2005 Society of Chemical IndustryThe supplementary material for this paper is now available at http://www.interscience.wiley.com/jpages/ 0268-2575/suppmat/

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Dithiol- and NAD-dependent degradation of epoxyalkanes by Xanthobacter Py2

Cited by 14 publications

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Carboxylation of epoxides to beta-keto acids in cell extracts of Xanthobacter strain Py2

Carboxylation of epoxides to beta-keto acids in cell extracts of Xanthobacter strain Py2

Involvement of an ATP-dependent carboxylase in a CO2-dependent pathway of acetone metabolism by Xanthobacter strain Py2

Utilisation of C₂–C₄ gaseous hydrocarbons and isoprene by microorganisms

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Dithiol- and NAD-dependent degradation of epoxyalkanes by Xanthobacter Py2

Cited by 14 publications

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Carboxylation of epoxides to beta-keto acids in cell extracts of Xanthobacter strain Py2

Carboxylation of epoxides to beta-keto acids in cell extracts of Xanthobacter strain Py2

Involvement of an ATP-dependent carboxylase in a CO2-dependent pathway of acetone metabolism by Xanthobacter strain Py2

Utilisation of C2–C4 gaseous hydrocarbons and isoprene by microorganisms

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Utilisation of C₂–C₄ gaseous hydrocarbons and isoprene by microorganisms