Browsing by Author "Strubel, Volker"

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Open Access
3-(2-hydroxyphenyl)catechol as substrate for proximal meta ring cleavage in dibenzofuran degradation by Brevibacterium sp. strain DPO 1361
(1991) Strubel, Volker; Engesser, Karl-Heinrich; Fischer, Peter; Knackmuss, Hans-Joachim
Brevibacterium sp. strain DPO 1361 oxygenates dibenzofuran in the unusual angular position. The 3-(2-hydroxyphenyl)catechol thus generated is subject to meta ring cleavage in the proximal position, yielding 2-hydroxy-6-(2-hydroxyphenyl)-6-oxo-2,4-hexadienoic acid, which is hydrolyzed to 2-oxo-4-pentenoate and salicylate by 2-hydroxy-6-oxo-6-phenyl-2,4-hexadienoic acid hydrolase. The proximal mode of ring cleavage is definitely established by isolation and unequivocal structural characterization of a cyclization product of 2-hydroxy-6-(2-hydroxyphenyl)-6-oxo-2,4-hexadienoic acid, i.e., 3-(chroman-4-on-2-yl)pyruvate.
Open Access
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.
Open Access
Dioxygenolytic cleavage of aryl ether bonds: 1,10-dihydro-1,10-dihydroxyfluoren-9-one, a novel arene dihydrodiol as evidence for angular dioxygenation of dibenzofuran
(1989) Engesser, Karl-Heinrich; Strubel, Volker; Christoglou, Konstantinos; Fischer, Peter; Rast, Hans G.
Two dibenzofuran degrading bacteria, Brevibacterium strain DPO 1361 and strain DPO 220, were found to utilize fluorene as sole source of carbon and energy. Cells which were grown on dibenzofuran, transformed fluorene into a number of products. For five of the seven metabolites isolated, the structure could be established unequivocally. Accumulation of one metabolite, 1,10-dihydroxy-1, 10-dihydrofluoren-9-one, indicated the presence of a novel type of dioxygenase, attacking polynuclear aromatic systems in the unusual angular position. Dibenzofuran degradation is proposed to likewise proceed via initial angular dioxygenation. Only aryl oxygen ether bond, which normally is extremely stable, is thus transformed to a hemiacetal. After spontaneous cleavage and subsequent rearomatization by dehydration, 2,2′,3-trihydroxybiphenyl [3-(2-hydroxyphenyl)-catechol] thus results as the immediate product of the first enzymatic reaction in the degradation sequence.
Open Access
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.
Open Access
Metabolism of dibenzofuran and dibenzodioxin as model for 2, 3, 7, 8-tetrachlorodibenzodioxin degradation
(1990) Strubel, Volker; Knackmuss, Hans-Joachim; Engesser, Karl-Heinrich
We demonstrated that fluorene and DBF are attacked hy strain DPO 1361 via an angular dioxygenation. A pathway for DBF degradation is presented, which inidicates an analogy to the pathway estahlished for diphenyl (1.4). Further investigations will have to show whether the same angular dioxygenation mechanism is involved also in the degradation of dibenzodioxin.
Open Access
Microbial degradation of biaryl structures: relationships between fluorene, dibenzofuran and biphenyl pathways
(1992) Trenz, Stefan Peter; Strubel, Volker; Knackmuss, Hans-Joachim; Engesser, Karl-Heinrich
Initial dioxygenation of fluorene by dibenzofuran degrading strains occurs in the unusual angular position. The resulting dihydrodiendiol is converted to 3-(2-carboxyphenyl)catechol by action of a dehydrogenase. This is a novel activity for a dehydrogenase causing a C-C-bond cleavage. After growth with dibenzofuran and biphenyl respectively two different initial dioxygenases are expressed. The first enzyme shows a broad substrate range, the second enzyme only converts biphenyl. Strains degrading fluorene, dibenzofuran and biphenyl may constitute a unique physiological group.
Open Access
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.