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PubMed2001

The antipsoriatic drug dimethylfumarate strongly suppresses chemokine production in human keratinocytes and peripheral blood mononuclear cells.

BACKGROUND: The effectiveness of systemic treatment of psoriasis with fumaric acid esters has been proven, but their mode of action at the cellular and molecular level has not yet been fully elucidated. OBJECTIVES: To study the effect of dimethylfumarate (DMF) on the production of the chemokines CXCL1, CXCL8, CXCL9, CXCL10 and CXCL11, formerly known as GROalpha, interleukin-8, Mig, IP-10 and IP-9/I-TAC, respectively, in human keratinocytes and peripheral blood mononuclear cells (PBMC). METHODS: Cultured keratinocytes were stimulated with interferon (IFN) -gamma to produce CXCL9, CXCL10 and CXCL11 and with phorbol myristate acetate to produce CXCL1 and CXCL8 in the absence and presence of DMF (5, 15 and 45 micromol L(-1)). PBMC were stimulated with either IFN-gamma to produce CXCL9 and CXCL10 or lipopolysaccharide to produce CXCL8, in the absence and presence of DMF (5, 15 and 45 micromol L(-1)). RNA preparations from isolated keratinocytes were analysed by Northern blotting; protein production by keratinocytes and PBMC was monitored by an enzyme-linked immunosorbent assay. RESULTS: Northern blot analysis on isolated keratinocyte RNA preparations showed a dose-dependent inhibition of CXCL1, CXCL8, CXCL9, CXCL10 and CXCL11 transcription by DMF. At 45 micromol L(-1) the inhibition was almost complete. In addition, keratinocytes and PBMC showed in the presence of DMF a dose-dependent inhibition of CXCL8, CXCL9 and CXCL10 protein production. CONCLUSIONS: These results show the ability of DMF to inhibit the production of chemokines that may be critically involved in the development and perpetuation of psoriatic lesions. This might explain, at least in part, the beneficial effects of treatment with fumaric acid esters in psoriasis patients.

Blotting, Northern↗
PubMed2001

Preferential expression of antioxidant response element mediated gene expression in astrocytes.

Transcriptional control of target genes by antioxidant/electrophile response elements has been well described in peripheral tissues. Genes that are regulated by this mechanism include the antioxidant enzymes NAD(P)H:quinone oxidoreductase, gamma-glutamyl cystine synthetase and glutathione-S-transferase. Antioxidant/electrophile response elements within a gene's promoter confer induction by low-molecular-weight electrophilic compounds such as tert-butylhydroquinone and dimethyl fumarate. We have now examined the ability of antioxidant/electrophile response elements to elicit gene expression in neurons and astrocytes in both brain slices and primary cultures using transient transfection of promoter reporter constructs. Our results using a heat-stable human placental alkaline phosphatase reporter indicate that antioxidant/electrophile response element mediated gene expression is largely restricted to astrocyte cell populations. Placental alkaline phosphatase expression was significantly elevated in astrocytes treated with the antioxidant/electrophile response element inducer dimethyl fumarate. Mutant constructs lacking a functional antioxidant/electrophile response element abolished all placental alkaline phosphatase expression in astrocytes. We suggest that astrocytic metabolic processes that normally aid and/or protect neurons may be controlled via this inducible system.

Animals↗
PubMed1986

Fumarase deficiency: a new cause of mitochondrial encephalomyopathy.

We observed a deficiency of both the mitochondrial and cytosolic forms of fumarase in a male infant with mitochondrial encephalomyopathy who presented at one month of age with failure to thrive, developmental delay, hypotonia, cerebral atrophy, lactic and pyruvic acidemia, and fumaric aciduria. The patient died at eight months of age. Isolated skeletal-muscle mitochondria showed selective defects in the oxidation of glutamate (31 ng atoms of oxygen consumed per minute per milligram of mitochondrial protein, as compared with 94 +/- 19 [mean +/- SD] in five controls) and of succinate (18 vs. 145 +/- 18 ng atoms of oxygen per minute per milligram of protein), whereas isolated liver mitochondria oxidized these and other substrates normally. Fumarase activity was virtually absent in both liver mitochondria (53 vs. 2878 +/- 248 nmol per minute per milligram of protein [5 controls]) and skeletal-muscle mitochondria (23 vs. 1997 +/- 717 nmol per minute per milligram [12 controls]). Seventeen other mitochondrial enzymes had normal activity in both liver and muscle mitochondrial extracts. Fumarase activity was also significantly reduced in homogenates of liver tissue (less than 1 vs. 90 +/- 25 mumol per minute per gram of wet weight [five controls]) and skeletal muscle (less than 1 vs. 21 +/- 4 mumol per minute per gram [five controls]), indicating a deficiency of both mitochondrial and cytosolic fumarases. Organ differences in intramitochondrial accumulation of fumarate may have accounted for the selective oxidative defects observed in the skeletal-muscle mitochondria but not liver mitochondria. All these findings are consistent with a profound combined fumarase deficiency.

Brain Diseases↗
PubMed1964

METABOLISM OF DICARBOXYLIC ACIDS IN ACETOBACTER XYLINUM.

Benziman, Moshe (The Hebrew University of Jerusalem, Jerusalem, Israel), and A. Abeliovitz. Metabolism of dicarboxylic acids in Acetobacter xylinum. J. Bacteriol. 87:270-277. 1964.-During the oxidation of fumarate or l-malate by whole cells or extracts of Acetobacter xylinum grown on succinate, a keto acid accumulated in the medium in considerable amounts. This acid was identified as oxaloacetic acid (OAA). No accumulation of OAA was observed when succinate served as substrate. These phenomena could be explained by the kinetics of malate, succinate, and OAA oxidation. OAA did not inhibit malate oxidation, even when present at high concentrations. When cells were incubated with OAA or fumarate in the presence of C(14)O(2), only the beta-carboxyl of residual OAA was found to be labeled. Evidence was obtained indicating that nicotinamide adenine dinucleotide (NAD) or nicotinamide adenine dinucleotide phosphate (NADP) are not directly involved in malate oxidation by cell-free extracts. The results suggest that malate oxidation in A. xylinum is irreversible, and is catalyzed by an enzyme which is not NAD- or NADP-linked.

Acetates↗
PubMed2006

Modest induction of phase 2 enzyme activity in the F-344 rat prostate.

BACKGROUND: Prostate cancer is the most commonly diagnosed malignancy in men and is thought to arise as a result of endogenous oxidative stress in the face of compromised carcinogen defenses. We tested whether carcinogen defense (phase 2) enzymes could be induced in the prostate tissues of rats after oral feeding of candidate phase 2 enzyme inducing compounds. METHODS: Male F344 rats were gavage fed sulforaphane, beta-naphthoflavone, curcumin, dimethyl fumarate or vehicle control over five days, and on the sixth day, prostate, liver, kidney and bladder tissues were harvested. Cytosolic enzyme activities of nicotinamide quinone oxidoreductase (NQO1), total glutathione transferase (using DCNB) and mu-class glutathione transferase (using CDNB) were determined in the treated and control animals and compared. RESULTS: In prostatic tissues, sulforaphane produced modest but significant increases in the enzymatic activities of NQO1, total GST and GST-mu compared to control animals. beta-naphthoflavone significantly increased NQO1 and GST-mu activities and curcumin increased total GST and GST-mu enzymatic activities. Dimethyl fumarate did not significantly increase prostatic phase 2 enzyme activity. Compared to control animals, sulforaphane also significantly induced NQO1 or total GST enzyme activity in the liver, kidney and, most significantly, in the bladder tissues. All compounds were well tolerated over the course of the gavage feedings. CONCLUSION: Orally administered compounds will induce modestly phase 2 enzyme activity in the prostate although the significance of this degree of induction is unknown. The 4 different compounds also altered phase 2 enzyme activity to different degrees in different tissue types. Orally administered sulforaphane potently induces phase 2 enzymes in bladder tissues and should be investigated as a bladder cancer preventive agent.

Animals↗
PubMed2001

[Effects of chemical agents on the prevention of fungal contamination during household wheat storage in Cixian county].

OBJECTIVE: To evaluate the effectiveness of several commercial chemical agents (DMF, AP and Chumeijing) on the prevention of fungal contamination in household storage of wheat in Cixian county. METHODS: The antifungal agents tested include dimethyl fumarate, DMF, aluminium phosphide, AP and Chumeijing (a Chinese product comprised of propionic acid, formic acid, sorbic acid and fumaric acid). The chemicals were applied in the wheat containers in the rural households. The fungal contamination and the inhibitory effects on fungal growth in wheat were measured by fungal isolation, culture, identification and count. RESULTS: The fungal contamination in the household wheat before using fungicides were quite common, with an overall contamination rate of 67.5% to 100%. The application of the three chemical fungicides effectively reduced fungal contamination in household stored wheat, and the effective rate for DMF, AP, AMF + AP and Chumeijing was 91.2%, 85.2%, 100% and 100% respectively, while the rate of fungi growth inhibition was (61.9 +/- 21.6)%, (64.0 +/- 21.6)%, (72.5 +/- 18.0)% and (63.1 +/- 24.3)% respectively. CONCLUSION: DMF, AP and Chumeijing are all effective in the prevention of fungal contamination for household stored wheat in Cixian county. AP is not recommended owing to its higher toxicity, compared with the other chemicals tested.

Acids, Acyclic↗
PubMed2003

Induction of NAD(P)H quinone: oxidoreductase1 inhibits carcinogen-induced aberrant crypt foci in colons of Sprague-Dawley rats.

Phase II detoxifying enzymes like NAD(P)H (quinone acceptor)oxidoreductase1 (NQO1), glutathione S-transferases (GST), and UDP-glucuronyltransferases (UGT) may play an important role in preventing carcinogen-induced cancers. Inducers of these enzymes have been shown to inhibit carcinogen-induced colon tumors in rat and mouse models. However, it has not been clearly demonstrated that NQO1 contributes to this effect. We examined the effect of NQO1 inducers on colon carcinogenesis using an aberrant crypt foci (ACF) rat model. Sprague-Dawley rats were fed control diet or diet containing 400 ppm dimethyl fumarate or 200 ppm oltipraz for 7 days, and Phase II enzymes in rat colon and liver were measured. Dimethyl fumarate significantly increased NQO1 and GST activities in colon and liver but did not increase UGT activities in these tissues. In contrast, oltipraz significantly increased NQO1 activities in colon and liver and produced a small increase in GST activity in the liver but did not increase GST activity in the colon or UGT activities in the liver or colon. Sprague Dawley rats were fed control diet or diet containing 200 ppm oltipraz and then treated with the carcinogens azoxymethane or methyl nitrosourea. Both carcinogens produced ACF in all of the rat colons, but rats fed oltipraz diet had significantly fewer ACF than those fed control diet. This protective effect was reversed in rats treated with the NQO1 inhibitor, dicoumarol. However, treatment with oltipraz did not alter the distribution of crypt multiplicities in the ACF. These studies demonstrated that induction of NQO1 plays a significant role in inhibiting initiation of carcinogen-induced ACF in Sprague-Dawley rats. This provides the first direct evidence that NQO1 may play a role in preventing colon cancer. The study also found that oltipraz added to the diet of Sprague-Dawley rats selectively increased NQO1 activity in colon mucosa with no increase in GST and UGT activities in these tissues. Thus, this model will be useful for further investigating the role of NQO1 in prevention of colon cancer.

Animals↗
PubMedDate not supplied

[Central metabolism in Acinetobacter sp. grown on ethanol].

The ethanol-grown cells of the mutant Acinetobacter sp. strain 1NG, incapable of producing exopolysaccharides, were analyzed for the activity of enzymes of the tricarboxylic acid (TCA) cycle and some biosynthetic pathways. In spite of the presence of both key enzymes (isocitrate lyase and malate synthase) of the glyoxylate cycle, these cells also contained all enzymes of the TCA cycle, which presumably serves biosynthetic functions. This was evident from the high activity of isocitrate dehydrogenase and glutamate dehydrogenase and the low activity of 2-oxoglutarate dehydrogenase. Pyruvate was formed in the reaction catalyzed by oxaloacetate decarboxylase, whereas phosphoenolpyruvate (PEP) was synthesized by the two key enzymes (PEP carboxykinase and PEP synthase) of gluconeogenesis. The proportion between these enzymes was different in the exponential and the stationary growth phases. The addition of the C4-dicarboxylic acid fumarate to the ethanol-containing growth medium led to a 1.5- to 2-fold increase in the activity of enzymes of the glyoxylate cycle, as well as of fumarate hydratase, malate dehydrogenase, PEP synthase, and PEP carboxykinase (the activity of the latter enzyme increased by more than 7.5 times). The data obtained can be used to improve the biotechnology of production of the microbial exopolysaccharide ethapolan on C2-substrates.

Acinetobacter↗
PubMed2004

Effect of biomaterial properties on bone healing in a rabbit tooth extraction socket model.

In this work we sought to understand the effect of biomaterial properties upon healing bone tissue. We hypothesized that a hydrophilic polymer gel implanted into a bone tissue defect would impede the healing process owing to the biomaterial's prevention of protein adsorption and thus cell adhesion. To test this hypothesis, healing bone was investigated within a rabbit incisor extraction socket, a subcritical size bone defect that resists significant soft tissue invasion by virtue of its conformity. After removal of the incisor teeth, one tooth socket was left as an empty control, one was filled with crosslinked polymer networks formed from the hydrophobic polymer poly(propylene fumarate) (PPF), and one was filled with a hydrogel formed from the hydrophilic oligomer oligo(poly(ethylene glycol) fumarate) (OPF). At five different times (4 days as well as 1, 2, 4, and 8 weeks), jaw bone specimens containing the tooth sockets were removed. We analyzed bone healing by histomorphometrical analysis of hematoxylin and eosin stained sections as well as immunohistochemically stained sections. The proposed hypothesis, that a hydrophilic material would hinder bone healing, was supported by the histomorphometrical results. In addition, the immunohistochemical results reflect molecular signaling indicative of the early invasion of platelets, the vascularization of wound-healing tissue, the differentiation of migrating progenitor cells, and the formation and remodeling of bone tissue. Finally, the results emphasize the need to consider biomaterial properties and their differing effects upon endogenous growth factors, and thus bone healing, during the development of tissue engineering devices.

Animals↗
PubMed2003

Use of stereolithography to manufacture critical-sized 3D biodegradable scaffolds for bone ingrowth.

A novel approach to the manufacture of biodegradable polymeric scaffolds for tissue-engineering utilizing stereolithography (SLA) is presented. SLA is a three-dimensional (3D) printing method that uses an ultraviolet laser to photo-crosslink a liquid polymer substrate. The current generation of SLA devices provide a 3D printing resolution of 0.1 mm. The experiments utilized a biodegradable resin mixture of diethyl fumarate (DEF), poly(propylene fumarate) (PPF), and a photoinitiator, bisacylphosphine oxide (BAPO). The PPF is crosslinked with the use of the SLA's UV laser (325-nm wavelength). An SLA device was retrofitted with a custom fixture build tank enclosing an elevator-driven build table. A 3D prototype model testing the manufacturing control this device provides was created in a computer-aided-design package. The resulting geometric data were used to drive the SLA process, and a DEF/PPF prototype part was successfully manufactured. These scaffolds have application in the tissue engineering of bony substrates.

Biocompatible Materials↗
PubMed2005

Derivatisation of carboxylic acid groups in pharmaceuticals for enhanced detection using liquid chromatography with electrospray ionisation tandem mass spectrometry.

Tris(2,4,6-trimethoxyphenyl)phosphonium propylamine bromide (TMPP) has been used for the derivatisation of maleic, fumaric, sorbic and salicylic acids to facilitate determination using liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/ESI-MS/MS) in positive ion mode. Detection limits, achieved using multiple reaction monitoring mode, were 2, 4, 0.4 and 540 fmol (5 muL injection) for derivatised fumaric, sorbic, maleic and salicylic acids, respectively. In comparison, detection limits achieved in negative ion mode for the underivatised acids were 24, 51, 2, and 117 fmol, respectively. The method was successfully used for the determination of sorbic acid in a sample of Panadol. The derivatisation of salicylic acid was not as successful, probably due to poor reaction efficiency.

Acetaminophen↗
PubMed1988

Differential roles for menaquinone and demethylmenaquinone in anaerobic electron transport of E. coli and their fnr-independent expression.

Escherichia coli grown with glucose in the absence of added electron acceptors contained 3-4 times more naphthoquinones (menaquinone plus demethylmenaquinone) than in the presence of O2. Presence of electron acceptors resulted in a slight additional increase of the naphthoquinone content. A strain defective in the fnr gene, which encodes the transcriptional activator of anaerobic respiration, showed the same response. With fumarate or dimethyl sulfoxide present, 94% of the naphthoquinones consisted of menaquinone, while with nitrate up to 78% was demethylmenaquinone. With trimethylamine N-oxid as the acceptor the proportion was intermediate. From the donor substrates of anaerobic respiration only glycerol had a significant influence on the ratio of the contents of the 2 quinones. It is concluded that FNR, the gene product of the fnr gene, is not required for anaerobic derepression of naphthoquinone biosynthesis. Menaquinone appears to be involved specifically in the respiration with fumarate or dimethyl sulfoxide, and demethylmenaquinone in nitrate respiration. Both naphthoquinones appear to serve in trimethylamine N-oxide respiration.

Anaerobiosis↗
PubMed1994

L-malic acid production by entrapped Saccharomyces cerevisiae into polyacrylamide gel beads.

The yeast Saccharomyces cerevisiae was entrapped within polyacrylamide gel beads by employing a procedure that uses sodium dodecylsulfate as a detergent to improve the spherical configuration of the beads. The resulting preparation showed a rate of fumarate bio-conversion to L-malic acid about 60 times higher than that found for the free cells. Almost all fumarate was converted in 30 min of incubation. The thermal stability of the immobilized cells did not significantly differ from the free cells. An optimal pH of 5.7 was found for the immobilized preparation and no succinic acid was detected as a byproduct in the incubation mixture.

Acrylic Resins↗
PubMed2005

Mitochondrial regulation of insulin production in rat pancreatic islets.

AIMS/HYPOTHESIS: The study was designed to identify the key metabolic signals of glucose-stimulated proinsulin gene transcription and translation, focusing on the mechanism of succinate stimulation of insulin production. METHODS: Wistar rat islets were incubated in 3.3 mmol/l glucose with and without esters of different mitochondrial metabolites or with 16.7 mmol/l glucose. Proinsulin biosynthesis was analysed by tritiated leucine incorporation into newly synthesised proinsulin. Preproinsulin gene transcription was evaluated following transduction with adenoviral vectors expressing the luciferase reporter gene under the control of the rat I preproinsulin promoter. Steady-state preproinsulin mRNA was determined using relative quantitative PCR. The mitochondrial membrane potential was measured by microspectrofluorimetry using rhodamine-123. RESULTS: Succinic acid monomethyl ester, but not other mitochondrial metabolites, stimulated preproinsulin gene transcription and translation. Similarly to glucose, succinate increased specific preproinsulin gene transcription and biosynthesis. The inhibitor of succinate dehydrogenase (SDH), 3-nitropropionate, abolished glucose- and succinate-stimulated mitochondrial membrane hyperpolarisation and proinsulin biosynthesis, indicating that stimulation of proinsulin translation depends on SDH activity. Partial inhibition of SDH activity by exposure to fumaric acid monomethyl ester abolished the stimulation of preproinsulin gene transcription, but only partially inhibited the stimulation of proinsulin biosynthesis by glucose and succinate, suggesting that SDH activity is particularly important for the transcriptional response to glucose. CONCLUSIONS/INTERPRETATION: Succinate is a key metabolic mediator of glucose-stimulated preproinsulin gene transcription and translation. Moreover, succinate stimulation of insulin production depends on its metabolism via SDH. The differential effect of fumarate on preproinsulin gene transcription and translation suggests that these processes have different sensitivities to metabolic signals.

Animals↗
PubMed2001

Anaerobic degradation of n-hexane in a denitrifying bacterium: further degradation of the initial intermediate (1-methylpentyl)succinate via C-skeleton rearrangement.

The anaerobic degradation pathway of the saturated hydrocarbon n-hexane in a denitrifying strain (HxN1) was examined by gas chromatography-mass spectrometry of derivatized extracts from cultures grown with unlabeled and deuterated substrate; several authentic standard compounds were included for comparison. The study was focused on possible reaction steps that follow the initial formation of (1-methylpentyl)succinate from n-hexane and fumarate. 4-Methyloctanoic, 4-methyloct-2-enoic, 2-methylhexanoic, 2-methylhex-2-enoic and 3-hydroxy-2-methylhexanoic acids (in addition to a few other methyl-branched acids) were detected in n-hexane-grown but not in n-hexanoate-grown cultures. Labeling indicated preservation of the original carbon chain of n-hexane in these acids. Tracing of the deuterium label of 3- d1-(1-methylpentyl)succinate in tentative subsequent products indicated a deuterium/carboxyl carbon exchange in the succinate moiety. This suggests that the metabolism of (1-methylpentyl)succinate employs reactions analogous to those in the established conversion of succinyl-CoA via methylmalonyl-CoA to propionyl-CoA. Accordingly, a pathway is proposed in which (1-methylpentyl)succinate is converted to the CoA-thioester, rearranged to (2-methylhexyl)malonyl-CoA and decarboxylated (perhaps by a transcarboxylase) to 4-methyloctanoyl-CoA. The other identified fatty acids match with a further degradation of 4-methyloctanoyl-CoA via rounds of conventional beta-oxidation. Such a pathway would also allow regeneration of fumarate (for n-hexane activation) from propionyl-CoA formed as intermediate and hence present a cyclic process.

Alkanes↗
PubMed1997

Environmental and physiological factors affecting the succinate product ratio during carbohydrate fermentation by Actinobacillus sp. 130Z.

Actinobacillus sp. 130Z fermented glucose to the major products succinate, acetate, and formate. Ethanol was formed as a minor fermentation product. Under CO2-limiting conditions, less succinate and more ethanol were formed. The fermentation product ratio remained constant at pH values from 6.0 to 7.4. More succinate was produced when hydrogen was present in the gas phase. Actinobacillus sp. 130Z grew at the expense of fumarate and l-malate reduction, with hydrogen as an electron donor. Other substrates such as more-reduced carbohydrates (e.g., d-sorbitol) resulted in higher succinate and/or ethanol production. Actinobacillus sp. 130Z contained the key enzymes involved in the Embden-Meyerhof-Parnas and the pentose-phosphate pathways and contained high levels of phosphoenolpyruvate (PEP) carboxykinase, malate dehydrogenase, fumarase, fumarate reductase, pyruvate kinase, pyruvate formate-lyase, phosphotransacetylase, acetate kinase, malic enzyme, and oxaloacetate decarboxylase. The levels of PEP carboxykinase, malate dehydrogenase, and fumarase were significantly higher in Actinobacillus sp. 130Z than in Escherichia coli K-12 and accounted for the differences in succinate production. Key enzymes in end product formation in Actinobacillus sp. 130Z were regulated by the energy substrates.

Actinobacillus↗
PubMed1998

Net efflux of citrate in Penicillium simplicissimum is mediated by a transport protein.

Penicillium simplicissimum excreted citrate, isocitrate, and succinate when grown in a strongly buffered medium [1 M Mes (pH 6) or 1 M Hepes (pH 7.3)]. Growth in a weakly buffered medium did not lead to citrate excretion despite a similar intracellular citrate concentration. When nongrowing, citrate-excreting hyphae were aerated in a glucose solution, the following steady-state intracellular concentrations of organic acids were measured: succinate (25 mM); citrate, isocitrate, malate, and fumarate (all less than 5 mM). After 2 h of incubation, the extracellular concentrations of these acids were [micromol (g dry wt.)-1]: isocitrate [100], citrate [60], succinate [30], and malate, fumarate, and alpha-ketoglutarate [<5]. The excretion of citrate was due neither to an unspecific change in the permeability of the plasma membrane nor to simple diffusion of undissociated citric acid. The involvement of a transport protein in citrate excretion was indicated because N-ethylmaleimide and sodium azide inhibited citrate excretion strongly despite an unchanged outward-directed citrate gradient. Arguments are given why efflux via a citrate uptake carrier is not considered probable. These results indicate that citrate is excreted by P. simplicissimum via a transport protein that probably specifically mediates the efflux of citrate.

Azides↗
PubMed2004

Anaerobic degradation of monoaromatic hydrocarbons.

Over the last two decades significant advances have been made in our understanding of the anaerobic biodegradability of monoaromatic hydrocarbons. It is now known that compounds such as benzene, toluene, ethylbenzene, and all three xylene isomers can be biodegraded in the absence of oxygen by a broad diversity of organisms. These compounds have been shown to serve as carbon and energy sources for bacteria growing phototrophically, or respiratorily with nitrate, manganese, ferric iron, sulfate, or carbon dioxide as the sole electron acceptor. In addition, it has also been recently shown that complete degradation of monoaromatic hydrocarbons can also be coupled to the respiration of oxyanions of chlorine such as perchlorate or chlorate, or to the reduction of the quinone moieties of humic substances. Many pure cultures of hydrocarbon-degrading anaerobes now exist and some novel biochemical and genetic pathways have been identified. In general, a fumarate addition reaction is used as the initial activation step of the catabolic process of the corresponding monoaromatic hydrocarbon compounds. However, other reactions may alternatively be involved depending on the electron acceptor utilized or the compound being degraded. In the case of toluene, fumarate addition to the methyl group mediated by benzylsuccinate synthase appears to be the universal mechanism of activation and is now known to be utilized by anoxygenic phototrophs, nitrate-reducing, Fe(III)-reducing, sulfate-reducing, and methanogenic cultures. Many of these biochemical pathways produce unique extracellular intermediates that can be utilized as biomarkers for the monitoring of hydrocarbon degradation in anaerobic natural environments.

Anaerobiosis↗