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Author: search.filters.author.Engesser, Karl-HeinrichSubject: search.filters.subject.570

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    Die Spaltung von Arylether-Bindungen durch initiale Dioxygenierung: Grundlage des bakteriellen Dioxinabbaus
    (1991) Engesser, Karl-Heinrich; Strubel, Volker; Kirchner, S.; Schestag, S.; Schulte, P.; Knackmuss, Hans-Joachim
    Bei der Untersuchung des bakteriellen Abbaus von Arylether-Modellsubstraten wie 2-Alkoxybenzoat, Carboxybiphenylether und Dibenzofuran wurde ein grundlegender Mechanismus für die Spaltung von Aryletherbindungen aufgedeckt. Demnach bewirken Dioxygenase-Enzyme unter Einführung zweier Hydroxylgruppen die Überführung von Ether- in Hemiacetalbindungen. Diese instabilen Hemiacetale reagieren unter Rearomatisierung zu aliphatischen Alkoholen und/oder Phenolverbindungen ab. Enzyme dieses Typs sind auch in der Lage, Dioxine zu spalten.
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    Microbial metabolism of chlorosalicylates: effect of prolonged subcultivation on constructed strains
    (1986) Rubio, Miguel Angel; Engesser, Karl-Heinrich; Knackmuss, Hans-Joachim
    The hybrid strain Pseudomonas sp. WR4016 was subcultivated with increasing concentrations of 5-chlorosalicylate (5rarr10 mM) as sole carbon source over a period of 9 months. At intervals of approximately 3 months derivative strains WR4017, WR4018 and WR4019 were isolated which exhibited higher growth rates and increased substrate tolerance. Comparative analysis of the turnover rates of the key enzymes in chlorosalicylate degradation showed that the adaptation process did not result from structural modifications of these proteins. Instead, balanced over-production of the salicylate hydroxylase and catechol 1,2-dioxygenase prevented the accumulation of toxic chlorocatechols and accounted for the reduction of the doubling times with 4- or 5-chlorosalicylate. A comparative analysis of a genetically engineered chlorosalicylate degrader PL300-1 showed similar regulatory patterns as the most advanced isolate WR4019 from the adaptation series.
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    Metabolism of 2-chloro-4-methylphenoxyacetate by Alcaligenes eutrophus JMP 134
    (1993) Pieper, Dietmar Helmut; Stadler-Fritzsche, Karin; Engesser, Karl-Heinrich; Knackmuss, Hans-Joachim
    2-Chloro-4-methylphenoxyacetate is not a growth substrate for Alcaligenes eutrophus JMP 134 and JMP 1341. It is, however, being transformed by enzymes of 2,4-dichlorophenoxyacetic acid metabolism to 2-chloro-4-methyl-cis, cis-muconate, which is converted by enzymatic 1,4-cycloisomerization to 4-carboxymethyl-2-chloro-4-methylmuconolactone as a dead end metabolite. Chemically, only 3,6-cycloisomerization occurs, giving rise to both diastereomers of 4-carboxychloromethyl-3-methylbut-2-en-4-olide. Those lactones harbonring a chlorosubstituent on the 4-carboxymethyl side chain were surprisingly stable under physiological as well as acidic conditions.
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    Degradation of 2-bromo-, 2-chloro- and 2-fluorobenzoate by Pseudomonas putida CLB 250
    (1989) Engesser, Karl-Heinrich; Schulte, P.
    Pseudomonas putida strain CLB 250 (DSM 5232) utilized 2-bromo-, 2-chloro- and 2-fluorobenzoate as sole source of carbon and energy. Degradation is suggested to be initiated by a dioxygenase liberating halide in the first catabolic step. After decarboxylation and rearomatization catechol is produced as a central metabolite which is degraded via the ortho-pathway. After inhibition of ring cleavage activities with 3-chlorocatechol, 2-chlorobenzoate was transformed to catechol in nearly stoichiometric amounts. Other ortho-substituted benzoates like anthranilate and 2-methoxybenzoate seem to be metabolized via the same route.
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    Assemblage of ortho cleavage route for simultaneous degradation of chloro- and methylaromatics
    (1987) Rojo, Fernando; Pieper, Dietmar H.; Engesser, Karl-Heinrich; Knackmuss, Hans-Joachim; Timmis, Kenneth N.
    Genetic engineering is a powerful means of accelerating the evolution of new biological activities and has considerable potential for constructing microorganisms that can degrade environmental pollutants. Critical enzymes from five different catabolic pathways of three distinct soil bacteria have been combined in patchwork fashion into a functional ortho cleavage route for the degradation of methylphenols and methylbenzoates. The new bacterium thereby evolved was able to degrade and grow on mixtures of chloro- and methylaromatics that were toxic even for the bacteria that could degrade the individual components of the mixtures. Except for one enzymatic step, the pathway was fully regulated and its component enzymes were only synthesized in response to the presence of pathway substrates.
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    Enrichment of dibenzofuran utilizing bacteria with high co-metabolic potential towards dibenzodioxin and other anellated aromatics
    (1989) Strubel, Volker; Rast, Hans G.; Fietz, Walter H.; Knackmuss, Hans-Joachim; Engesser, Karl-Heinrich
    Dibenzofuran degrading bacteria were enriched from various environmental sources. A mutualistic mixed culture of strain DPO 220 and strain DPO 230 was characterized. Strain DPO 220 alone showed limited growth with dibenzofuran as sole source of carbon and energy (td ≥ 4.5 h). A labile degradation product, C12H10O5, and salicylate were isolated from the culture fluid. Salicylate was found to be a central intermediate of DBF-degradation.Strain DPO 220 co-metabolized a wide range of anellated aromatics as well as heteroaromatics. High rates of co-oxidation of dibenzodioxin demonstrate analogue-enrichment to be a powerful technique for selecting enzymatic activities for otherwise non-degradable substrates.
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    Simultaneous degradation of chloro- and methylaromatics via ortho pathway by genetically engineered bacteria and natural soil isolates
    (1989) Engesser, Karl-Heinrich; Pieper, Dietmar H.; Rojo, Fernando; Timmis, Kenneth N.; Knackmuss, Hans-Joachim
    The simultaneous bacterial metabolism of chloro- and methylaromatics via ortho- or metapathway, normally results in incomplete degradation and death of the organisms. This is caused by misrouting of central intermediates. i.e. substituted catechols into unproductive pathways and suicide inactivation of the key enzyme of meta pathway, (catechol 2,3-dioxygenase). The meta pathway proved to be definitely unsuited for productive metabolism of chloroaromatics. Therefore two strategies were used for simultaneous degradation of mixtures of chloro- and methylaromatics via ortho pathways: Methyllactons or certain mixtures of chloro- and methylaromatics were used as enrichment substrates, yielding strains which metabolized these compounds almost exclusively via the desired pathway. Alternatively relevant enzymes from five different catabolic pathways of three distinct soil bacteria were combined in a patchwork fashion generating a functional ortho cleavage route for methylaromatics coexisting with the ortho cleavage pathway of chloroaromatics.
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    Bacterial metabolism of side chain fluorinated aromatics: cometabolism of 4-trifluoromethyl(TFM)-benzoate by 4-isopropylbenzoate grown Pseudomonas putida JT strains
    (1988) Engesser, Karl-Heinrich; Rubio, Miguel Angel; Ribbons, Douglas W.
    Enzymes of the p-cymene pathway in Pseudomonas putida strains cometabolized the intermediate analogue 4-trifluoromethyl(TFM)benzoate. Three products, 4-TFM-2,3-dihydro-2,3-dihydroxybenzoate, 4-TFM-2,3-dihydroxy-benzoate and 2-hydroxy-6-oxo-7,7,7-trifluorohepta-2,4-dienoate (7-TFHOD) were identified chemically and by spectroscopic proterties.Certain TFM-substituted analogue metabolites of the p-cymene pathway were transformed at drastically reduced rates. Hammett type analysis of ring cleavage reactions of 4-substituted 2,3-dihydroxybenzoates revealed the negative inductive and especially mesomeric effect of substituents to be rate determining. Whereas decarboxylation of 3-carboxy-7-TFHOD was not affected by fluorine substitution the subsequent hydrolysis of 7-TFHOD proceeded very slowly. The negative inductive effect of the TFM-group probably inhibited heterolysis of the carbon bond between C5 and C6 of 7-TFHOD.
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    (+)-4-Carboxymethyl-2,4-dimethylbut-2-en-4-olide as dead-end metabolite of 2,4-dimethylphenoxyacetic acid or 2,4-dimethylphenol by alcaligenes eutrophus JMP 134
    (1990) Pieper, Dietmar H.; Engesser, Karl-Heinrich; Knackmuss, Hans-Joachim
    2,4-Dimethylphenoxyacetic acid and 2,4-dimethylphenol are not growth substrates for Alcaligenes eutrophus JMP 134 although being cooxidized by 2,4-dichlorophenoxyacetate grown cells. None of the relevant catabolic pathways were induced by the dimethylphenoxyacetate, 3,5-Dimethylcatechol is not subject to metacleavage. The alternative ortho-eleavage is also unproductive and gives rise to (+)-4-carboxymethyl-2,4-dimethylbut-2-en-4-olide as a dead-end metabolite. High yields of this metabolite were obtained with the mutant Alcaligenes eutrophys JMP 134-1 which constitutively expresses the genes of 2,4-dichlorophenoxyacetic acid metabolism.
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    Der Abbau von Modellstrukturen der Kohle: Stoffwechselweg des Dibenzofuran- und Fluorenabbaus
    (1991) Engesser, Karl-Heinrich; Strubel, Volker; Trenz, Stefan Peter; Rothe, Bernd; Schmid, Andreas; Knackmuss, Hans-Joachim
    Several microorganisms have been isolated degrading structural elements of coal like dibenzofuran. fluorene and biphenyl. Extensive investigation of the degradation pathways revealed a common mechanism of initial attack. Although catalyzed by different enzymes, all three substrates are converted to 3-phenyl-substituted catechols, which, after meta-cleavage are transformed to simple aromatic structures like salicylate, phthalate and benzoate. This ring cleaving enzymes have been cloned and are further analyzed after subcloning. Two different initial dioxygenases seem to be present in some strains cataIyzing ether cleavage of dibenzofuran and oxygenation of biphenyl respectively. Attempts are presently made to clone the first enzyme in order to produce higher yields of its optically active products. Some of these compounds have been characterized and may be of commercial value as fine chemicals.