Chemical structure and biodegradability of halogenated aromatic compounds. Conversion of chlorinated muconic acids into maleoylacetic acid.
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ABSTRACT:
SUBMITTER: Schmidt E
PROVIDER: S-EPMC1162339 | biostudies-other | 1980 Oct
REPOSITORIES: biostudies-other
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Project description:Substituted muconic acids were prepared from the corresponding catechols by pyrocatechase II from Pseudomonas sp. B13. The stabilities of substituted muconic acids were compared under different pH conditions. 3-Substituted cis, cis-muconic acids cycloisomerized readily in slightly acidic solutions, whereas 2-chloro- and 2-fluoro-cis,cis-muconic acids were stable under these conditions and could be isolated as crystalline compounds. They were isomerized to the cis, trans-form in highly acidic solution (pH 1), particularly when heated to 80 degrees C. Cycloisomerization of 2-chloro-cis,cis-muconic acid in 75% (v/v) H2SO4 yields 4-carboxymethyl-2-chloro-but-2-en-4-olide (4-chloro-2,5-dihydro-5-oxo-3H-furan-2-ylacetic acid). THe cis,cis-configuration of 2-chloromuconic acid was certified by 1H n.m.r. spectroscopy and by enzymic cycloisomerization. Although the cis,cis-configuration of 2-fluoromuconic acid was confirmed by corresponding spectroscopic data, it was not cycloisomerized by crude extracts or cycloisomerase II preparations from Pseudomonas sp. B13.
| S-EPMC1162338 | biostudies-other
Project description:1. The influence of halogen substituents on the 1,2-dioxygenation of catechols was investigated. The results obtained with the two isoenzymes pyrocatechase I and pyrocatechase II from the haloarene-utilizing Pseudomonas sp. B 13 and the pyrocatechase from benzoate-induced cells of Alcaligenes eutrophus B.9 were compared. 2. Substituents on catechol were found to interfere with O2 binding by the two isoenzymes from Pseudomonas sp. B 13, whereas the Km value for catechol kept constant at different O2 concentrations. 3. Electron-attracting substituents decreased the Km values for catechols. 4. Results from binding studies with substituted catechols demonstrated narrow stereospecificities of pyrocatechase I from pseudomonas sp. B 13 and the pyrocatechase from alcaligenes eutrophus B.9. In contrast, a low steric hindrance by substituents in the binding of catechols with pyrocatechase II was observed. 5. Low pK'1 values of substituted catechols resulted in low Michaelis constants. 6. Electron-attracting substituents such as halogen decreased the reaction rates of catechol 1,2-dioxygenation. The correlation of the Vmax. values observed with pyrocatechase II from Pseudomonas sp. B 13 with the substituent constant sigma+ (Okamoto--Brown equation) was distinctly greater than with Hammett's sigma values. The corresponding logVmax. against sigma+ correlation for pyrocatechase I was considerably disturbed by steric influences of the substituents.
| S-EPMC1185888 | biostudies-other
Project description:1. Two catechol 1,2-dioxygenases, pyrocatechase I and pyrocatechase II, were found in 3-chlorobenzoate-grown cells of Pseudomonas sp. B 13. The latter enzyme showed high relative activities with 3- and 4-chlorocatechol compared with catechol. 2. In benzoate-grown cells, only pyrocatechase I was induced. It was purified 29-fold with a final specific activity of 20 mumol of catechol oxygenated/min per mg of protein and an overall yield of 22%. Because of the instability of pyrocatechase II on chromatography and dialysis, no increase of specific activity was obtained during the purification experiments. 3. Molecular weights of pyrocatechase I and pyrocatechase II were 82000 and 67000 respectively. 4. For both pyrocatechases the pH optimum was found to be at 8.0.5. Inhibitions of the two pyrocatechases by Cu2+ and Hg2+ ions and p-chloromercuribenzoate were different. The effect on pyrocatechase I after incubation for 20 h with the heavy metals was decreased by addition of 1 mM-2-mercaptoethanol to the reaction mixture. The inhibition of pyrocatechase II was even enhanced under these conditions. 6. Extradiol cleavage of 3-methylcatechol in addition to intradiol fission at a ratio of 1:14 was observed only with pyrocatechase I.
| S-EPMC1185887 | biostudies-other
Project description:The iodination of chlorinated aromatic compounds using Ag(2)SO(4)/I(2), AgSbF(6)/I(2), AgBF(4)/I(2) and AgPF(6)/I(2) offers access to iodoarenes that are valuable intermediates in organic synthesis. Specifically, iodination of phenols, anisoles and anilines with a 3,5-dichloro substitution pattern preferentially yielded the ortho, para and para iodinated product, respectively. In the case of chlorobenzene and 3-chlorotoluene, AgSbF(6)/I(2), AgBF(4)/I(2) and AgPF(6)/I(2), but not Ag(2)SO(4)/I(2), selectively introduced the iodine in para position to the chlorine substituent.
| S-EPMC3170769 | biostudies-literature
Project description:Biodegradability describes the capacity of substances to be mineralized by free-living bacteria. It is a crucial property in estimating a compound's long-term impact on the environment. The ability to reliably predict biodegradability would reduce the need for laborious experimental testing. However, this endpoint is difficult to model due to unavailability or inconsistency of experimental data. Our approach makes use of the Online Chemical Modeling Environment (OCHEM) and its rich supply of machine learning methods and descriptor sets to build classification models for ready biodegradability. These models were analyzed to determine the relationship between characteristic structural properties and biodegradation activity. The distinguishing feature of the developed models is their ability to estimate the accuracy of prediction for each individual compound. The models developed using seven individual descriptor sets were combined in a consensus model, which provided the highest accuracy. The identified overrepresented structural fragments can be used by chemists to improve the biodegradability of new chemical compounds. The consensus model, the datasets used, and the calculated structural fragments are publicly available at http://ochem.eu/article/31660.
| S-EPMC5175213 | biostudies-literature
Project description:Compound biodegradability tests with natural microbial communities form an important keystone in the ecological assessment of chemicals. However, biodegradability tests are frequently limited by a singular focus either on the chemical and potential transformation products or on the individual microbial species degrading the compound. Here, we investigated a methodology to simultaneously analyze community compositional changes and biomass growth on dosed test compound from flow cytometry (FCM) data coupled to machine-learned cell type recognition. We quantified the growth of freshwater microbial communities on a range of carbon dosages of three readily biodegradable reference compounds, phenol, 1-octanol, and benzoate, in comparison to three fragrances, methyl jasmonate, myrcene, and musk xylene (as a nonbiodegradable control). Compound mass balances with between 0.1 to 10 mg C · liter-1 phenol or 1-octanol, inferred from cell numbers, parent compound analysis, and CO2 evolution, as well as use of 14C-labeled compounds, showed between 6 and 25% mg C · mg C-1 substrate incorporation into biomass within 2 to 4 days and 25 to 45% released as CO2 In contrast, similar dosage of methyl jasmonate and myrcene supported slower (4 to 10 days) and less (2.6 to 6.6% mg C · mg C-1 with 4.9 to 22% CO2) community growth. Community compositions inferred from machine-learned cell type recognition and 16S rRNA amplicon sequencing showed substrate- and concentration-dependent changes, with visible enrichment of microbial subgroups already at 0.1 mg C · liter-1 phenol and 1-octanol. In general, community compositions were similar at the start and after the stationary phase of the microbial growth, except at the highest used substrate concentrations of 100 to 1,000 mg C · liter-1 Flow cytometry cell counting coupled to deconvolution of communities into subgroups is thus suitable to infer biodegradability of organic chemicals, permitting biomass balances and near-real-time assessment of relevant subgroup changes.IMPORTANCE The manifold effects of potentially toxic compounds on microbial communities are often difficult to discern. Some compounds may be transformed or completely degraded by few or multiple strains in the community, whereas others may present inhibitory effects. In this study, we benchmark a new method based on machine-learned microbial cell recognition to rapidly follow dynamic changes in aquatic communities. We further determine productive biodegradation upon dosing of a number of well-known readily biodegradable tester compounds at a variety of concentrations. Microbial community growth was quantified using flow cytometry, and the multiple cell parameters measured were used in parallel to deconvolute the community on the basis of similarity to previously standardized cell types. Biodegradation was further confirmed by chemical analysis, showing how distinct changes in specific populations correlate to degradation. The method holds great promise for near-real-time community composition changes and deduction of compound biodegradation in natural microbial communities.
| S-EPMC7883543 | biostudies-literature
Project description:Polyhalogenated aromatic compounds are harmful environmental contaminants and tend to persist in anoxic soils and sediments. Dehalococcoides mccartyi strain DCMB5, a strain originating from dioxin-polluted river sediment, was examined for its capacity to dehalogenate diverse chloroaromatic compounds. Strain DCMB5 used hexachlorobenzenes, pentachlorobenzenes, all three tetrachlorobenzenes, and 1,2,3-trichlorobenzene as well as 1,2,3,4-tetra- and 1,2,4-trichlorodibenzo-p-dioxin as electron acceptors for organohalide respiration. In addition, 1,2,3-trichlorodibenzo-p-dioxin and 1,3-, 1,2-, and 1,4-dichlorodibenzo-p-dioxin were dechlorinated, the latter to the nonchlorinated congener with a remarkably short lag phase of 1 to 4 days following transfer. Strain DCMB5 also dechlorinated pentachlorophenol and almost all tetra- and trichlorophenols. Tetrachloroethene was dechlorinated to trichloroethene and served as an electron acceptor for growth. To relate selected dechlorination activities to the expression of specific reductive dehalogenase genes, the proteomes of 1,2,3-trichlorobenzene-, pentachlorobenzene-, and tetrachloroethene-dechlorinating cultures were analyzed. Dcmb_86, an ortholog of the chlorobenzene reductive dehalogenase CbrA, was the most abundant reductive dehalogenase during growth with each electron acceptor, suggesting its pivotal role in organohalide respiration of strain DCMB5. Dcmb_1041 was specifically induced, however, by both chlorobenzenes, whereas 3 putative reductive dehalogenases, Dcmb_1434, Dcmb_1339, and Dcmb_1383, were detected only in tetrachloroethene-grown cells. The proteomes also harbored a type IV pilus protein and the components for its assembly, disassembly, and secretion. In addition, transmission electron microscopy of DCMB5 revealed an irregular mode of cell division as well as the presence of pili, indicating that pilus formation is a feature of D. mccartyi during organohalide respiration.
| S-EPMC4277595 | biostudies-literature
Project description:1. Halogen analogues of p-nitrobenzoate and benzoate were oxidized by washed cells of Nocardia erythropolis. 2. The oxidation of 2-fluoro-4-nitrobenzoate ceased at the level of acetate, and fluoroacetate was found in the incubation medium and particularly in hot-ethanolic extracts of the cells. 3. Several fluorine-containing intermediates were detected and 2-fluoroprotocatechuate was identified as one of them. 4. The nitro group was also reduced by the organism, as evidenced by the formation of 4-amino-2-fluorobenzoate. 5. Extracts of N. erythropolis activated fluoroacetate and condensed the resulting fluoroacetyl-CoA with oxaloacetate to form fluorocitrate. This product was a very powerful inhibitor of citrate metabolism by guinea-pig kidney homogenates and of the aconitase also present in the bacterial extracts. The inhibitions effected by synthetic fluorocitrate and the natural product were comparable. 6. 2-Fluoro-4-nitrobenzoate had negligible mammalian toxicity. 7. The isolation of fluoroacetate as a product of 2-fluoro-4-nitrobenzoate oxidation implies that the aromatic ring in this bacterium must be degraded via a gamma-carboxymuconolactone; fluoroacetate cannot arise by metabolism through the isomeric beta-carboxymuconolactone.
| S-EPMC1198488 | biostudies-other
Project description:An aerobic dieldrin-degrading fungus, Mucor racemosus strain DDF, and two aerobic endosulfan-degrading fungal strains, Mortierella sp. strains W8 and Cm1-45, were isolated from soil contaminated with organochlorine pesticides. Strain DDF degraded more than 90% dieldrin during 10-days of incubation at 25°C and showed the production of a small amount of aldrin trans-diol. Moreover, strain DDF reduced levels of aldrin trans-diol while producing unknown metabolites that were determined to be aldrin trans-diol exo- and endo-phosphates. On the other hand, Mortierella sp. strains W8 and Cm1-45 degraded more than 70% and 50% of α and β-endosulfan, respectively, over 28 days at 25°C, in liquid cultures containing initial concentrations of 8.2 µM of each substance. Only a small amount of endosulfan sulfate, a persistent metabolite, was detected in the both cultures, while these strains could not degrade endosulfan sulfate when this compound was provided as the initial substrate. Both strains generate endosulfan diol as a first step in the degradation of endosulfan, then undergo further conversion to endosulfan lactone.
| S-EPMC6265662 | biostudies-literature
Project description:In lactococci, transamination is the first step of the enzymatic conversion of aromatic and branched-chain amino acids to aroma compounds. In previous work we purified and biochemically characterized the major aromatic aminotransferase (AraT) of a Lactococcus lactis subsp. cremoris strain. Here we characterized the corresponding gene and evaluated the role of AraT in the biosynthesis of amino acids and in the conversion of amino acids to aroma compounds. Amino acid sequence homologies with other aminotransferases showed that the enzyme belongs to a new subclass of the aminotransferase I subfamily gamma; AraT is the best-characterized representative of this new aromatic-amino-acid-specific subclass. We demonstrated that AraT plays a major role in the conversion of aromatic amino acids to aroma compounds, since gene inactivation almost completely prevented the degradation of these amino acids. It is also highly involved in methionine and leucine conversion. AraT also has a major physiological role in the biosynthesis of phenylalanine and tyrosine, since gene inactivation weakly slowed down growth on medium without phenylalanine and highly affected growth on every medium without tyrosine. However, another biosynthesis aromatic aminotransferase is induced in the absence of phenylalanine in the culture medium.
| S-EPMC91656 | biostudies-literature