共查询到20条相似文献,搜索用时 31 毫秒
1.
The sulfate-reducing highly enriched culture N47 is capable to anaerobically degrade naphthalene, 2-methylnaphthalene, and
2-naphthoic acid. A proteogenomic investigation was performed to elucidate the initial activation reaction of anaerobic naphthalene
degradation. This lead to the identification of an alpha-subunit of a carboxylase protein that was two-fold up-regulated in
naphthalene-grown cells compared to 2-methylnaphthalene-grown cells. The putative naphthalene carboxylase subunit showed 48%
similarity to the anaerobic benzene carboxylase from an iron-reducing, benzene-degrading culture and 45% to alpha-subunit
of phenylphosphate carboxylase of Aromatoleum aromaticum EbN1. A gene for the beta-subunit of putative naphthalene carboxylase was located nearby on the genome and was expressed
with naphthalene. Similar to anaerobic benzene carboxylase, there were no genes for gamma- and delta-subunits of a putative
carboxylase protein located on the genome which excludes participation in degradation of phenolic compounds. The genes identified
for putative naphthalene carboxylase subunits showed only weak similarity to 4-hydroxybenzoate decarboxylase excluding ATP-independent
carboxylation. Several ORFs were identified that possibly encode a 2-naphthoate-CoA ligase, which is obligate for activation
before the subsequent ring reduction by naphthoyl-CoA reductase. One of these ligases was exclusively expressed on naphthalene
and 2-naphthoic acid and might be the responsible naphthoate-CoA-ligase. 相似文献
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Anaerobic phenol metabolism was studied in three facultative aerobic denitrifying bacteria, Thauera aromatica, “Aromatoleum aromaticum” strain EbN1 (Betaproteobacteria), and Magnetospirillum sp. (Alphaproteobacterium). All species formed phenylphosphate and contained phenylphosphate carboxylase but not phenol carboxylase
activity. This is in contrast to direct phenol carboxylation by fermenting bacteria. Antisera raised against subunits of the
Thauera phenylphosphate synthase and phenylphosphate carboxylase partly cross-reacted with the corresponding proteins in the other
species. Some unsolved features of phenylphosphate carboxylase were addressed in T. aromatica. The core sub-complex of this enzyme consists of three different subunits and catalyzes the exchange of 14CO2 with the carboxyl group of 4-hydroxybenzoate, but not phenylphosphate carboxylation. It was inactivated by oxygen or by the
oxidizing agent thionin and fully reactivated under reducing conditions. The purified recombinant phosphatase subunit alone
had only low phenylphosphate phosphatase activity in the absence of the other components. However, activity was strongly enhanced
in the presence of the core enzyme resulting in phenylphosphate carboxylation. Hence, a tight interaction of the carboxylase
subunits is required for dephosphorylation of phenylphosphate, which is coupled to the concomitant carboxylation of the produced
phenolate to 4-hydroxybenzoate, thus preventing a futile cycle. 相似文献
4.
Dorjee G. Tamang Ralf Rabus Ravi D. Barabote Milton H. SaierJr. 《The Journal of membrane biology》2009,229(2):53-90
The denitrifying bacterium “Aromatoleum aromaticum” strain EbN1 is specialized for the aerobic utilization of aromatic compounds including crude oil constituents. We here report
whole-genome analyses for potential transport proteins in A. aromaticum strain EbN1. This organism encodes very few transporters for simple sugars and most other common carbon sources. However,
up to 28% of its putative transporters may act on fairly hydrophobic aromatic and aliphatic compounds. We categorize the putative
transporters encoded within the genome, assign them to recognized families, and propose their preferred substrates. The bioinformatic
data are correlated with available metabolic information to obtain an integrated view of the metabolic network of A. aromaticum strain EbN1. The results thus indicate that this organism possesses a disproportionately large percentage of transporters
for the uptake and efflux of hydrophobic and amphipathic aromatic and aliphatic compounds compared with previously analyzed
organisms. We predict that these findings will have important implications for our ecophysiological understanding of bioremediation. 相似文献
5.
The genome of Syntrophorhabdus aromaticivorans strain UI provides new insights for syntrophic aromatic compound metabolism and electron flow 下载免费PDF全文
Masaru K. Nobu Takashi Narihiro Tamaki Hideyuki Yan‐Ling Qiu Yuji Sekiguchi Tanja Woyke Lynne Goodwin Karen W. Davenport Yoichi Kamagata Wen‐Tso Liu 《Environmental microbiology》2015,17(12):4861-4872
How aromatic compounds are degraded in various anaerobic ecosystems (e.g. groundwater, sediments, soils and wastewater) is currently poorly understood. Under methanogenic conditions (i.e. groundwater and wastewater treatment), syntrophic metabolizers are known to play an important role. This study explored the draft genome of Syntrophorhabdus aromaticivorans strain UI and identified the first syntrophic phenol‐degrading phenylphosphate synthase (PpsAB) and phenylphosphate carboxylase (PpcABCD) and syntrophic terephthalate‐degrading decarboxylase complexes. The strain UI genome also encodes benzoate degradation through hydration of the dienoyl‐coenzyme A intermediate as observed in Geobacter metallireducens and Syntrophus aciditrophicus. Strain UI possesses electron transfer flavoproteins, hydrogenases and formate dehydrogenases essential for syntrophic metabolism. However, the biochemical mechanisms for electron transport between these H2/formate‐generating proteins and syntrophic substrate degradation remain unknown for many syntrophic metabolizers, including strain UI. Analysis of the strain UI genome revealed that heterodisulfide reductases (HdrABC), which are poorly understood electron transfer genes, may contribute to syntrophic H2 and formate generation. The genome analysis further identified a putative ion‐translocating ferredoxin : NADH oxidoreductase (IfoAB) that may interact with HdrABC and dissimilatory sulfite reductase gamma subunit (DsrC) to perform novel electron transfer mechanisms associated with syntrophic metabolism. 相似文献
6.
Phthaloyl‐coenzyme A decarboxylase from Thauera chlorobenzoica: the prenylated flavin‐, K+‐ and Fe2+‐dependent key enzyme of anaerobic phthalate degradation 下载免费PDF全文
Mario Mergelsberg Max Willistein Heike Meyer Hans‐Joachim Stärk Dominique F. Bechtel Antonio J. Pierik Matthias Boll 《Environmental microbiology》2017,19(9):3734-3744
The degradation of the industrially produced and environmentally relevant phthalate esters by microorganisms is initiated by the hydrolysis to alcohols and phthalate (1,2‐dicarboxybenzene). In the absence of oxygen the further degradation of phthalate proceeds via activation to phthaloyl‐CoA followed by decarboxylation to benzoyl‐CoA. Here, we report on the first purification and characterization of a phthaloyl‐CoA decarboxylase (PCD) from the denitrifying Thauera chlorobenzoica. Hexameric PCD belongs to the UbiD‐family of (de)carboxylases and contains prenylated FMN (prFMN), K+ and, unlike other UbiD‐like enzymes, Fe2+ as cofactors. The latter is suggested to be involved in oxygen‐independent electron‐transfer during oxidative prFMN maturation. Either oxidation to the Fe3+‐state in air or removal of K+ by desalting resulted in >92% loss of both, prFMN and decarboxylation activity suggesting the presence of an active site prFMN/Fe2+/K+‐complex in PCD. The PCD‐catalysed reaction was essentially irreversible: neither carboxylation of benzoyl‐CoA in the presence of 2 M bicarbonate, nor an isotope exchange of phthaloyl‐CoA with 13C‐bicarbonate was observed. PCD differs in many aspects from prFMN‐containing UbiD‐like decarboxylases and serves as a biochemically accessible model for the large number of UbiD‐like (de)carboxylases that play key roles in the anaerobic degradation of environmentally relevant aromatic pollutants. 相似文献
7.
o‐Phthalate derived from plastics’ plasticizers and a bacterium's solution to its anaerobic degradation 下载免费PDF全文
R. G. Sawers 《Molecular microbiology》2018,108(6):595-600
Phthalic acid esters (phthalates) are anthropogenic compounds that are used as plasticizers. Unfortunately, because phthalates are non‐covalently intercalated into plastic polymers they leach into the environment, accumulating in anoxic sediments. This has negative consequences for animal and human health. Denitrifying Betaproteobacteria, such as Aromatoleum aromaticum, can use ortho‐phthalate, derived by ester hydrolysis, as a carbon and energy source. Mergelsberg et al. ( 2018 ) deconstruct the pathway whereby ortho‐phthalic acid is converted, via the highly unstable phthaloyl‐CoA, to the central intermediate of anaerobic aromatic degradation, benzoyl‐CoA. The latter reaction is catalysed by UbiD‐like phthaloyl‐CoA decarboxylase (PCD). Succinyl‐CoA:o‐phthalate CoA‐transferase (SPT) generates phthaloyl‐CoA, which accumulates at only sub‐micromolar concentrations, while the Km of PCD for phthaloyl‐CoA is two‐orders of magnitude higher. This seemingly insurmountable kinetic barrier is overcome because A. aromatoleum massively over‐produces PCD and because the decarboxylation reaction is irreversible. These features of the pathway facilitate capture of phthaloyl‐CoA as it is released from SPT without the need for direct substrate‐channelling. The authors provide strong evidence from both in vivo and in vitro studies to support their conclusions. This work reveals how these anaerobic bacteria have rapidly evolved a stop‐gap measure to allow them to completely degrade an otherwise recalcitrant aromatic xenobiotic. 相似文献
8.
Integration of chemotaxis,transport and catabolism in Pseudomonas putida and identification of the aromatic acid chemoreceptor PcaY 下载免费PDF全文
Rita A. Luu Joshua D. Kootstra Vasyl Nesteryuk Ceanne N. Brunton Juanito V. Parales Jayna L. Ditty Rebecca E. Parales 《Molecular microbiology》2015,96(1):134-147
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Ralf Rabus Kathleen Trautwein Lars Wöhlbrand 《Applied microbiology and biotechnology》2014,98(8):3371-3388
The denitrifying betaproteobacterium “Aromatoleum aromaticum” EbN1 is a well-studied model organism for anaerobic degradation of aromatic compounds. Following publication of its genome in 2005, comprehensive physiological–proteomic studies were conducted to deduce functional understanding from the genomic blueprint. A catabolic network (85 predicted, 65 identified proteins) for anaerobic degradation of 24 aromatic growth substrates (including 11 newly recognized) was established. Newly elucidated pathways include those for 4-ethylphenol and plant-derived 3-phenylpropanoids, involving functional assignment of several paralogous genes. The substrate-specific regulation of individual peripheral degradation pathways is probably initiated by highly specific chemical sensing via dedicated sensory/regulatory proteins, e.g. three different σ54-dependent one-component sensory/regulatory proteins are predicted to discriminate between three phenolic substrates (phenol, p-cresol and 4-ethylphenol) and two different two-component systems are assumed to differentiate between two alkylbenzenes (toluene, ethylbenzene). Investigations under in situ relevant growth conditions revealed (a) preferred utilization of benzoate from a mixture with succinate results from repressed synthesis of a C4-dicarboxylate TRAP transporter; (b) response to alkylbenzene-induced solvent stress comprises metabolic re-routing of acetyl-CoA and reducing equivalents to poly(3-hydroxybutyrate) synthesis, alteration of cellular membrane composition and formation of putative solvent efflux systems; and (c) multifaceted adaptation to slow growth includes adjustment of energy demand for maintenance and preparedness for future nutritional opportunities, i.e. provision of uptake systems and catabolic enzymes for multiple aromatic substrates despite their absence. This broad knowledge base taken together with the recent development of a genetic system will facilitate future functional, biotechnological (stereospecific dehydrogenases) and habitat re-enacting (“eco-”systems biology) studies with “A. aromaticum” EbN1. 相似文献
11.
So-Jeong Kim Soo-Je Park Man-Young Jung Jong-Geol Kim Eugene L. Madsen Sung-Keun Rhee 《Applied and environmental microbiology》2014,80(10):3233-3243
Stable isotope probing (SIP) is a cultivation-free methodology that provides information about the identity of microorganisms participating in assimilatory processes in complex communities. In this study, a Herminiimonas-related bacterium was identified as the dominant member of a denitrifying microcosm fed [13C]toluene. The genome of the uncultivated toluene-degrading bacterium was obtained by applying pyrosequencing to the heavy DNA fraction. The draft genome comprised ∼3.8 Mb, in 131 assembled contigs. Metabolic reconstruction of aromatic hydrocarbon (toluene, benzoate, p-cresol, 4-hydroxybenzoate, phenylacetate, and cyclohexane carboxylate) degradation indicated that the bacterium might specialize in anaerobic hydrocarbon degradation. This characteristic is novel for the order Burkholderiales within the class Betaproteobacteria. Under aerobic conditions, the benzoate oxidation gene cluster (BOX) system is likely involved in the degradation of benzoate via benzoyl coenzyme A. Many putative genes for aromatic hydrocarbon degradation were closely related to those in the Rhodocyclaceae (particularly Aromatoleum aromaticum EbN1) with respect to organization and sequence similarity. Putative mobile genetic elements associated with these catabolic genes were highly abundant, suggesting gene acquisition by Herminiimonas via horizontal gene transfer. 相似文献
12.
The denitrifying “Aromatoleum aromaticum” strain EbN1 was demonstrated to utilize p-ethylphenol under anoxic conditions and was suggested to employ a degradation pathway which is reminiscent of known anaerobic ethylbenzene degradation in the same bacterium: initial hydroxylation of p-ethylphenol to 1-(4-hydroxyphenyl)-ethanol followed by dehydrogenation to p-hydroxyacetophenone. Possibly, subsequent carboxylation and thiolytic cleavage yield p-hydroxybenzoyl-coenzyme A (CoA), which is channeled into the central benzoyl-CoA pathway. Substrate-specific formation of three of the four proposed intermediates was confirmed by gas chromatographic-mass spectrometric analysis and also by applying deuterated p-ethylphenol. Proteins suggested to be involved in this degradation pathway are encoded in a single large operon-like structure (~15 kb). Among them are a p-cresol methylhydroxylase-like protein (PchCF), two predicted alcohol dehydrogenases (ChnA and EbA309), a biotin-dependent carboxylase (XccABC), and a thiolase (TioL). Proteomic analysis (two-dimensional difference gel electrophoresis) revealed their specific and coordinated upregulation in cells adapted to anaerobic growth with p-ethylphenol and p-hydroxyacetophenone (e.g., PchF up to 29-fold). Coregulated proteins of currently unknown function (e.g., EbA329) are possibly involved in p-ethylphenol- and p-hydroxyacetophenone-specific solvent stress responses and related to other aromatic solvent-induced proteins of strain EbN1. 相似文献
13.
Genes involved in anaerobic degradation of the petroleum hydrocarbon ethylbenzene in the denitrifying Azoarcus-like strain EbN1 were identified on a 56-kb DNA contig obtained from shotgun sequencing. Ethylbenzene is first oxidized via ethylbenzene dehydrogenase to (S)-1-phenylethanol; this is converted by (S)-1-phenylethanol dehydrogenase to acetophenone. Further degradation probably involves acetophenone carboxylase forming benzoylacetate, a ligase forming benzoylacetyl-CoA, and a thiolase forming acetyl-CoA and benzoyl-CoA. Genes of this pathway were identified via N-terminal sequences of proteins isolated from strain EbN1 and by sequence similarities to proteins from other bacteria. Ethylbenzene dehydrogenase is encoded by three genes (ebdABC), in accordance with the heterotrimeric enzyme structure. Binding domains for a molybdenum cofactor (in subunit EbdA) and iron/sulfur-clusters (in subunits EbdA and EbdB) were identified. The previously observed periplasmic location of the enzyme was corroborated by the presence of a twin-arginine leader peptide characteristic of the Tat system for protein export. A fourth gene (ebdD) was identified, the product of which may act as an enzyme-specific chaperone in the maturation of the molybdenum-containing subunit. A distinct gene (ped) coding for (S)-1-phenylethanol dehydrogenase apparently forms an operon with the ebdABCD genes. The ped gene product with its characteristic NAD(P)-binding motif in the N-terminal domain belongs to the short-chain dehydrogenase/reductase (SDR) superfamily. A further operon apparently contains five genes (apc1-5) suggested to code for subunits of acetophenone carboxylase. Four of the five gene products are similar to subunits of acetone carboxylase from Xanthobacter autotrophicus. Upstream of the apc genes, a single gene (bal) was identified which possibly codes for a benzoylacetate CoA-ligase and which is co-transcribed with the apc genes. In addition, an apparent operon containing almost all genes required for beta-oxidation of fatty acids was detected; one of the gene products may be involved in thiolytic cleavage of benzoylacetyl-CoA. The DNA fragment also included genes for regulatory systems; these were two sets of two-component systems, two LysR homologs, and a TetR homolog. Some of these proteins may be involved in ethylbenzene-dependent gene expression. 相似文献
14.
Bastian Greshake Simonida Zehr Francesco Dal Grande Anjuli Meiser Imke Schmitt Ingo Ebersberger 《Molecular ecology resources》2016,16(2):511-523
Whole‐genome shotgun sequencing of multispecies communities using only a single library layout is commonly used to assess taxonomic and functional diversity of microbial assemblages. Here, we investigate to what extent such metagenome skimming approaches are applicable for in‐depth genomic characterizations of eukaryotic communities, for example lichens. We address how to best assemble a particular eukaryotic metagenome skimming data, what pitfalls can occur, and what genome quality can be expected from these data. To facilitate a project‐specific benchmarking, we introduce the concept of twin sets, simulated data resembling the outcome of a particular metagenome sequencing study. We show that the quality of genome reconstructions depends essentially on assembler choice. Individual tools, including the metagenome assemblers Omega and MetaVelvet, are surprisingly sensitive to low and uneven coverages. In combination with the routine of assembly parameter choice to optimize the assembly N50 size, these tools can preclude an entire genome from the assembly. In contrast, MIRA, an all‐purpose overlap assembler, and SPAdes, a multisized de Bruijn graph assembler, facilitate a comprehensive view on the individual genomes across a wide range of coverage ratios. Testing assemblers on a real‐world metagenome skimming data from the lichen Lasallia pustulata demonstrates the applicability of twin sets for guiding method selection. Furthermore, it reveals that the assembly outcome for the photobiont Trebouxia sp. falls behind the a priori expectation given the simulations. Although the underlying reasons remain still unclear, this highlights that further studies on this organism require special attention during sequence data generation and downstream analysis. 相似文献
15.
Initial reactions of anaerobic metabolism of alkylbenzenes in denitrifying and sulfate-reducing bacteria 总被引:13,自引:0,他引:13
The initial activation reactions of anaerobic oxidation of the aromatic hydrocarbons toluene and ethylbenzene were investigated
in cell extracts of a toluene-degrading, sulfate-reducing bacterium, Desulfobacula toluolica, and in cell extracts of strain EbN1, a denitrifying bacterium capable of degrading toluene and ethylbenzene. Extracts of
toluene-grown cells of both species catalysed the addition of fumarate to the methyl group of [phenyl-14C]-toluene and formed [14C]-labeled benzylsuccinate. Extracts of ethylbenzene-grown cells of strain EbN1 did not catalyse this reaction, but catalysed
the formation of 1-phenylethanol and acetophenone from [methylene-14C]-ethylbenzene. Toluene-grown cells of D. toluolica and strain EbN1 synthesised highly induced polypeptides corresponding to the large subunits of benzylsuccinate synthase from
Thauera aromatica. These polypeptides were absent in strain EbN1 after growth on ethylbenzene, although a number of different polypeptides
were highly induced. Thus, formation of benzylsuccinate from toluene and fumarate appears to be the general initiating step
in anaerobic toluene degradation by bacteria affiliated with the phylogenetically distinct β-subclass (strain EbN1 and T. aromatica) and δ-subclass (D. toluolica) of the Proteobacteria. Anaerobic ethylbenzene oxidation proceeds via a different pathway involving a two-step oxidation
of the methylene group to an alcohol and an oxo group; these steps are most probably followed by a biotin-independent carboxylation
reaction and thiolytic cleavage.
Received: 16 March 1998 / Accepted: 27 June 1998 相似文献
16.
Steffi Herrmann Sabine Kleinsteuber Antonis Chatzinotas Steffen Kuppardt Tillmann Lueders Hans‐Hermann Richnow Carsten Vogt 《Environmental microbiology》2010,12(2):401-411
The flow of carbon under sulfate‐reducing conditions within a benzene‐mineralizing enrichment culture was analysed using fully labelled [13C6]‐benzene. Over 180 days of incubation, 95% of added 13C‐benzene was released as 13C‐carbon dioxide. DNA extracted from cultures that had degraded different amounts of unlabelled or 13C‐labelled benzene was centrifuged in CsCl density gradients to identify 13C‐benzene‐assimilating organisms by density‐resolved terminal restriction fragment length polymorphism analysis and cloning of 16S rRNA gene fragments. Two phylotypes showed significantly increased relative abundance of their terminal restriction fragments in ‘heavy’ fractions of 13C‐benzene‐incubated microcosms compared with a 12C‐benzene‐incubated control: a member of the Cryptanaerobacter/Pelotomaculum group within the Peptococcaceae, and a phylotype belonging to the Epsilonproteobacteria. The Cryptanaerobacter/Pelotomaculum phylotype was the most frequent sequence type. A small amount of 13C‐methane was aceticlastically produced, as concluded from the linear relationship between methane production and benzene degradation and the detection of Methanosaetaceae as the only methanogens present. Other phylotypes detected but not 13C‐labelled belong to several genera of sulfate‐reducing bacteria, that may act as hydrogen scavengers for benzene oxidation. Our results strongly support the hypothesis that benzene is mineralized by a consortium consisting of syntrophs, hydrogenotrophic sulfate reducers and to a minor extent of aceticlastic methanogens. 相似文献
17.
The acylneuraminate lyase gene from Clostridium perfringens A99 was cloned on a 3.3 kb HindIII DNA fragment identified by screening the chromosomal DNA of this species by hybridization with an oligonucleotide probe
that had been deduced from the N-terminal amino acid sequence of the purified protein, and another probe directed against
a region that is conserved in the acylneuraminate lyase gene of Escherichia coli and in the putative gene of Clostridium tertium. After cloning, three of the recombinant clones expressed lyase activity above the background of the endogenous enzyme of
the E. coli host. The sequenced part of the cloned fragment contains the complete acylneuraminate lyase gene (ORF2) of 864 bp that encodes
288 amino acids with a calculated molecular weight of 32.3 kDa. The lyase structural gene follows a non-coding region with
an inverted repeat and a ribosome binding site. Upstream from this regulatory region another open reading frame (ORF1) was
detected. The 3′-terminus of the lyase structural gene is followed by a further ORF (ORF3). A high homology was found between
the amino acid sequences of the sialate lyases from Clostridium perfringens and Haemophilus influenzae (75% identical amino acids) or Trichomonas vaginalis (69% identical amino acids), respectively, whereas the similarity to the gene from E. coli is low (38% identical amino acids). Based on our new sequence data, the ‘large’ sialidase gene and the lyase gene of C. perfringens are not arranged next to each other on the chromosome of this species.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
18.
Rabus R 《Applied microbiology and biotechnology》2005,68(5):580-587
Nitrate-reducing bacteria of the recently recognized Azoarcus/Thauera group within the Betaproteobacteria contribute significantly to the biodegradation of aromatic and other refractory compounds in anoxic waters and soils. Strain EbN1 belongs to a distinct cluster (new genus) and is the first member of this phylogenetic group, the genome of which has been determined (4.7 Mb; one chromosome, two plasmids) by [Rabus R, Kube M, Heider J, Beck A, Heitmann K, Widdel F, Reinhardt R (2005) The genome sequence of an anaerobic aromatic-degrading denitrifying bacterium, strain EbN1. Arch Microbiol 183:27–36]. Ten anaerobic and four aerobic aromatic-degradation pathways were recognized on the chromosome, with the coding genes mostly forming clusters. Presence of paralogous gene clusters (e.g. for anaerobic ethylbenzene degradation) suggests an even broader degradation spectrum than previously known. Metabolic versatility is also reflected by the presence of multiple respiratory complexes and is apparently controlled by an extensive regulatory network. Strain EbN1 is unique for its capacity to degrade toluene and ethylbenzene anaerobically via completely different pathways. Bioinformatical analysis of their genetic blueprints and global expression analysis (DNA-microarray and proteomics) of substrate-adapted cells [Kühner S, Wöhlbrand L, Fritz I, Wruck W, Hultschig C, Hufnagel P, Kube M, Reinhardt R, Rabus R (2005) Substrate-dependent regulation of anaerobic degradation pathways for toluene and ethylbenzene in a denitrifying bacterium, strain EbN1. J Bacteriol 187:1493–1503] indicated coordinated vs sequential modes of regulation for the toluene and ethylbenzene pathways, respectively. 相似文献
19.
The anaerobic metabolism of catechol (1,2-dihydroxybenzene) was studied in the betaproteobacterium Thauera aromatica that was grown with CO2 as a cosubstrate and nitrate as an electron acceptor. Based on different lines of evidence and on our knowledge of enzymes and genes involved in the anaerobic metabolism of other aromatic substrates, the following pathway is proposed. Catechol is converted to catechylphosphate by phenylphosphate synthase, which is followed by carboxylation by phenylphosphate carboxylase at the para position to the phosphorylated phenolic hydroxyl group. The product, protocatechuate (3,4-dihydroxybenzoate), is converted to its coenzyme A (CoA) thioester by 3-hydroxybenzoate-CoA ligase. Protocatechuyl-CoA is reductively dehydroxylated to 3-hydroxybenzoyl-CoA, possibly by 4-hydroxybenzoyl-CoA reductase. 3-Hydroxybenzoyl-CoA is further metabolized by reduction of the aromatic ring catalyzed by an ATP-driven benzoyl-CoA reductase. Hence, the promiscuity of several enzymes and regulatory proteins may be sufficient to create the catechol pathway that is made up of elements of phenol, 3-hydroxybenzoate, 4-hydroxybenzoate, and benzoate metabolism. 相似文献
20.
Makoto Kawamukai 《Bioscience, biotechnology, and biochemistry》2016,80(1):23-33
Coenzyme Q (CoQ) is a component of the electron transport chain that participates in aerobic cellular respiration to produce ATP. In addition, CoQ acts as an electron acceptor in several enzymatic reactions involving oxidation–reduction. Biosynthesis of CoQ has been investigated mainly in Escherichia coli and Saccharomyces cerevisiae, and the findings have been extended to various higher organisms, including plants and humans. Analyses in yeast have contributed greatly to current understanding of human diseases related to CoQ biosynthesis. To date, human genetic disorders related to mutations in eight COQ biosynthetic genes have been reported. In addition, the crystal structures of a number of proteins involved in CoQ synthesis have been solved, including those of IspB, UbiA, UbiD, UbiX, UbiI, Alr8543 (Coq4 homolog), Coq5, ADCK3, and COQ9. Over the last decade, knowledge of CoQ biosynthesis has accumulated, and striking advances in related human genetic disorders and the crystal structure of proteins required for CoQ synthesis have been made. This review focuses on the biosynthesis of CoQ in eukaryotes, with some comparisons to the process in prokaryotes. 相似文献