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41.
42.
Polycyclic aromatic hydrocarbon (PAH) o-quinone reductase (PQR) plays a crucial role in the detoxification of PAH o-quinones by reducing them to catechols. Two constitutive PQRs were found in cell extracts of a pyrene-degrading Mycobacterium sp. strain PYR100. The enzymes had an activity towards 9,10-phenanthrenequinone (PQ) and/or 4,5-pyrenequinone (PyQ), and the relative amounts varied with the pH of the culture media. PQR1, containing an FAD cofactor, was a monomer (20.1 kDa), and PQR2, with no flavin cofactor, was a homodimer (26.5 kDa subunits). There was no homology between the N-terminal sequences of PQR1 and PQR2. Dicumarol and quercetin inhibited PQR2 more strongly than PQR1. PQR1 had much lower specificity constants (k(cat)/K(m), 10(5)M(-1)s(-1)) for menadione (0.80) and PQ (5.19) than PQR2 (13.9 for menadione and 176 for PQ). Additionally, PQR2 exhibited a broad substrate specificity with high specificity constants for 1,4-naphthalenequinone, 1,2-naphthalenequinone, and PyQ. 相似文献
43.
The TOL plasmid-encoded enzymes of the methyl-benzoate pathway in Pseudomonas putida mt-2 cometabolized 3-trifluoromethyl (TFM)-benzoate. Two products, 3-TFM-1,2-dihydroxy-2-hydrobenzoate (3-TFM-DHB) and 2-hydroxy-6-oxo-7,7,7-trifluoro-hepta-2,4-dienoate (7-TFHOD) were identified chemically and by spectroscopic properties. TFM-substituted analogues of the metabolites of the methylbenzoate pathway were generally converted at drastically reduced rates. The catechol-2,3-dioxygenase from Pseudomonas putida showed moderate turnover rates with 3-TFM-catechol. The catechol-1,2-dioxygenase of Rhodococcus rubropertinctus N657 was totally inhibited by 3-TFM-catechol and did not cleave this substrate. Hammett-type analysis showed the catechol-1,2-dioxygenase reaction to be strongly dependent on the electronic nature of the substituents. Electronegative substituents strongly inhibited catechol cleavage. The catechol-2,3-dioxygenase reaction, however, was only moderately sensitive to electronegative substituents. 相似文献
44.
M. Megharaj S. Hartmans K.-H. Engesser J. H. Thiele 《Applied microbiology and biotechnology》1998,49(3):337-342
1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) is the peri-chlorinated derivative of 1,1-diphenylethylene (DPE). Biodegradation of DDE and DPE
by bacteria has so far not been shown. Pure cultures of aerobic bacteria involved in biodegradation of styrene and polychlorinated
biphenyls (PCB) were therefore screened for their ability to degrade or cometabolize DPE and DDE. Styrene-metabolizing bacteria
(Rhodococcus strains S5 and VLB150) grew with DPE as their sole source of carbon and energy. Polychlorinated-biphenyl-degrading bacteria
(Pseudomonas fluorescens and Rhodococcus globerulus) were unable to degrade DPE even in the presence of an easily utilizable cosubstrate, biphenyl. This is the first report
of the utilization of DPE as sole carbon and energy source by bacteria. All the tested bacteria failed to degrade DDE when
it was provided as the sole carbon source or in the presence of the respective degradable cosubstrates. DPE transformation
could also be detected in cell-free extracts of Rhodococcus S5 and VLB150, but DDE was not transformed, indicating that cell wall and membrane diffusion barriers were not limiting biodegradation.
The results of the present study show that, at least for some bacteria, the chlorination of DDE is the main reason for its
resistance to biodegradation by styrene and DPE-degrading bacteria.
Received: 28 May 1997 / Received revision: 28 October 1997 / Accepted: 31 October 1997 相似文献
45.
Uwe Dehmel Karl-Heinrich Engesser Kenneth N. Timmis Daryl F. Dwyer 《Archives of microbiology》1995,163(1):35-41
Pseudomonas pseudoalcaligenes strain POB310 degrades 3-and 4-carboxydiphenyl ether. The initial reaction involves an angular dioxygenation yielding an unstable hemiacetal that spontaneously decays to phenol and protocatechuate. We cloned a DNA fragment containing the gene encoding the initial, dioxygenase from an unstable, self-transmissible plasmid. Sequence analysis revealed two open reading frames encoding proteins with putative molecular masses of 46.3 and 33.6 kDa. The deduced amino acid sequences showed homologies to oxygenase and reductase subunits of aromatic ring-activating dioxygenases, and contained regions identical to consensus sequences that bind chloroplast-like and Rieske-type [2Fe2S] clusters suggesting that the initial dioxygenase is a class IA aromatic ring-activating dioxygenase system. Intitial dioxygenase activity was induced in bacteria grown in M9 minimal medium containing 3-or 40-carboxydiphenyl ether or phenol as carbon source, indicating that the regulation is dependent on the phenol pathway. The maximal specific activity was measured at the beginning of the exponential growth phase. 相似文献
46.
47.
D.H. Pieper K.-H. Engesser R.H. Don K.N. Timmis H.-J. Knackmuss 《FEMS microbiology letters》1985,29(1-2):63-67
Abstract 2,4-Dichlorophenoxyacetate-grown cells of Alcaligenes eutrophus JMP134 [1] metabolized 4-methylphenoxyacetate via a modified ortho -cleavage pathway. 4-Carboxymethyl-4-methylbut-2-en-1,4-olide (4-methyl-2-enelactone), 4-carboxymethyl-3-methylbut-2-en-1,4-olide (3-methyl-2-enelactone) and 4-methyl-3-oxoadipate, were identified as intermediates. 相似文献
48.
The time courses of sesquiterpenoid phytoalexin accumulation were examined in compatible and incompatible interactions of leaves and tubers from five different R genotypes of potato (Solanum tuberosum) with corresponding pathotypes of Phytophthora infestans, as well as in non-host interactions of all five potato cultivars with Phytophthora megasperma f. sp. glycinea and in elicitor-treated tubers from five, and cell suspension cultures from two, of the cultivars. In tubers, rishitin and several structurally related sesquiterpene derivatives accumulated rapidly in non-host incompatible interactions, less rapidly in host incompatible interactions, and more slowly in compatible interactions. Treatment of tubers or cell cultures with fungal culture filtrate or arachidonic acid elicited in most cases a transient accumulation of the sesquiterpenoid phytoalexins. None of these compounds was detectable under any of the applied conditions either in infected or in elicitortreated leaves. Sesquiterpenoid phytoalexins might therefore be helpful, but appear not to be essential, in disease resistance of potato.Abbreviations CF
concentrated culture filtrate of Pi
- cv.
cultivar
-
Pi
Phytophthora infestans (numbering indicates pathotypes corresponding to R genes in potato)
-
Pmg
Phytophthora megasperma f. sp. glycinea 相似文献
49.
Adaptation of Alcaligenes eutrophus B9 and Pseudomonas sp. B13 to 2-Fluorobenzoate as Growth Substrate 总被引:7,自引:5,他引:2 下载免费PDF全文
Alcaligenes eutrophus B9 and Pseudomonas sp. B13 could be adapted to 2-fluorobenzoate as the sole source of carbon and energy. The ability of the A. eutrophus B9 to use this new substrate is clearly based on the defective dihydrodihydroxybenzoate dehydrogenase. Nontoxic 6-fluoro-3,5-cyclohexadiene-1,2-diol-1-carboxylic acid is accumulated instead of 3-fluorocatechol. About 84% of the substrate is dioxygenated to catechol and utilized via the 3-oxoadipate pathway. During continuous adaptation of Pseudomonas sp. B13 regioselectivity of dioxygenation of 2-fluorobenzoate is drastically changed in favor of a 1,2-attack. Consequently, approximately 97% of the substrate is utilized via catechol. A three- to fourfold overproduction of key enzymes of the 3-oxoadipate pathway compensates for the slower turnover rates of the fluorinated substrates. 相似文献
50.
Karl-Heinrich Engesser Miguel Angel Rubio Hans-Joachim Knackmuss 《Applied microbiology and biotechnology》1990,32(5):600-608
Summary Sixteen bacterial strains capable of degrading alkylbenzenes and alkylphenols were directly isolated from soil and water. The degradation pathways are discussed. Alkylcatechols are almost exclusively cleaved via meta-ring fission. Meta-cleavage of 3-trifluoromethyl-(TFM)-catechol was observed with all strains at different rates although the reaction rates compared to catechol as a substrate varied considerably. All 2-hydroxy-6-oxohepta-2,4-dienoic acid hydrolases investigated showed strong binding of 7,7,7-trifluoro-2-hydroxy-6-oxohepta-2,4-dienoic acid, the ring fission product of 3-TFM-catechol. Turnover rates, however, were negligible indicating this compound to be a general dead-end metabolite during metabolism of TFM-substituted compounds via meta-cleavage pathways.Offprint requests to: K.-H. Engesser 相似文献