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1.
Mycobacterium tuberculosis ( Mtb) is an aerobic bacterium that persists intracellularly in host macrophages and has evolved diverse mechanisms to combat and survive oxidative stress. Here we show a novel F 420‐dependent anti‐oxidant mechanism that protects Mtb against oxidative stress. Inactivation of the fbiC gene in Mtb results in a cofactor F 420‐deficient mutant that is hypersensitive to oxidative stress and exhibits a reduction in NADH/NAD + ratios upon treatment with menadione. In agreement with the recent hypothesis on oxidative stress being an important component of the pathway resulting in cell death by bactericidal agents, F 420? mutants are hypersensitive to mycobactericidal agents such as isoniazid, moxifloxacin and clofazimine that elevate oxidative stress. The Mtb deazaflavin‐dependent nitroreductase (Ddn) and its two homologues Rv1261c and Rv1558 encode for an F 420H 2‐dependent quinone reductase (Fqr) function leading to dihydroquinones. We hypothesize that Fqr proteins catalyse an F 420H 2‐specific obligate two‐electron reduction of endogenous quinones, thereby competing with the one‐electron reduction pathway and preventing the formation of harmful cytotoxic semiquinones, thus protecting mycobacteria against oxidative stress and bactericidal agents. These findings open up an avenue for the inhibition of the F 420 biosynthesis pathway or Fqr‐class proteins as a mechanism to potentiate the action of bactericidal agents. 相似文献
2.
Bilirubin is a potent antioxidant that is produced from the reduction of the heme degradation product biliverdin. In mammalian cells and Cyanobacteria, NADH/NADPH‐dependent biliverdin reductases (BVRs) of the Rossmann‐fold have been shown to catalyze this reaction. Here, we describe the characterization of Rv2074 from Mycobacterium tuberculosis, which belongs to a structurally and mechanistically distinct family of F 420H 2‐dependent BVRs (F‐BVRs) that are exclusively found in Actinobacteria. We have solved the crystal structure of Rv2074 bound to its cofactor, F 420, and used this alongside molecular dynamics simulations, site‐directed mutagenesis and NMR spectroscopy to elucidate its catalytic mechanism. The production of bilirubin by Rv2074 could exploit the anti‐oxidative properties of bilirubin and contribute to the range of immuno‐evasive mechanisms that have evolved in M. tuberculosis to allow persistent infection. 相似文献
3.
Cofactor F420, a 5-deazaflavin involved in obligatory hydride transfer, is widely distributed among archaeal methanogens and actinomycetes. Owing to the low redox potential of the cofactor, F420-dependent enzymes play a pivotal role in central catabolic pathways and xenobiotic degradation processes in these organisms. A physiologically essential deazaflavoenzyme is the F420-dependent glucose-6-phosphate dehydrogenase (FGD), which catalyzes the reaction F420 + glucose-6-phosphate → F420H2 + 6-phospho-gluconolactone. Thereby, FGDs generate the reduced F420 cofactor required for numerous F420H2-dependent reductases, involved e.g., in the bioreductive activation of the antitubercular prodrugs pretomanid and delamanid. We report here the identification, production, and characterization of three FGDs from Rhodococcus jostii RHA1 (Rh-FGDs), being the first experimental evidence of F420-dependent enzymes in this bacterium. The crystal structure of Rh-FGD1 has also been determined at 1.5 Å resolution, showing a high similarity with FGD from Mycobacterium tuberculosis (Mtb) (Mtb-FGD1). The cofactor-binding pocket and active-site catalytic residues are largely conserved in Rh-FGD1 compared with Mtb-FGD1, except for an extremely flexible insertion region capping the active site at the C-terminal end of the TIM-barrel, which also markedly differs from other structurally related proteins. The role of the three positively charged residues (Lys197, Lys258, and Arg282) constituting the binding site of the substrate phosphate moiety was experimentally corroborated by means of mutagenesis study. The biochemical and structural data presented here provide the first step towards tailoring Rh-FGD1 into a more economical biocatalyst, e.g., an F420-dependent glucose dehydrogenase that requires a cheaper cosubstrate and can better match the demands for the growing applications of F420H2-dependent reductases in industry and bioremediation. 相似文献
4.
Methanogenic archaea growing on ethanol or isopropanol as the electron donor for CO 2 reduction to CH 4 contain either an NADP-dependent or a coenzyme F 420-dependent alcohol dehydrogenase. We report here that in both groups of methanogens, the N
5, N
10-methylenetetrahydromethanopterin dehydrogenase and the N
5, N
10-methylenetetrahydromethanopterin reductase, two enzymes involved in CO 2 reduction to CH 4, are specific for F 420. This raised the question how F 420H 2 is regenerated in the methanogens with an NADP-dependent alcohol dehydrogenase. We found that these organisms contain catabolic
activities of an enzyme catalyzing the reduction of F 420 with NADPH. The F 420-dependent NADP reductase from Methanogenium organophilum was purified and characterized. The N-terminal amino acid sequence showed 42% sequence identity to a putative gene product
in Methanococcus jannaschii, the total genome of which has recently been sequenced.
Received: 12 May 1997 / Accepted: 1 July 1997 相似文献
5.
Washed membranes prepared from H 2+CO 2- or formate-grown cells of Methanococcus voltae catalyzed the oxidation of coenzyme F 420H 2 and the reduction of the heterodisulfide (CoB–S–S–CoM) of 2-mercaptoethanesulfonate and 7-mercaptoheptanoylthreonine phosphate,
which is the terminal electron acceptor of the methanogenic pathway. The reaction followed a 1:1 stoichiometry according to
the equation: F 420H 2 + COB–S–S–CoM → F 420 + CoM–SH + CoB–SH. These findings indicate that the reaction depends on a membrane-bound F 420H 2-oxidizing enzyme and on the heterodisulfide reductase, which remains partly membrane-bound after cell lysis. To elucidate
the nature of the F 420H 2-oxidizing protein, washed membranes were solubilized with detergent, and the enzyme was purified by sucrose density centrifugation,
anion-exchange chromatography, and gel filtration. Several lines of evidence indicate that F 420H 2 oxidation is catalyzed by a membrane-associated F 420-reducing hydrogenase. The purified protein catalyzed the H 2-dependent reduction of methyl viologen and F 420. The apparent molecular mass and the subunit composition (43, 37, and 27 kDa) are almost identical to those of the F 420-reducing hydrogenase that has already been purified from Mc. voltae. Moreover, the N-terminus of the 37-kDa subunit is identical to the amino acid sequence deduced from the fruG gene of the operon encoding the selenium-containing F 420-reducing hydrogenase from Mc. voltae. A distinct F 420H 2 dehydrogenase, which is present in methylotrophic methanogens, was not found in this organism.
Received: 18 September 1998 / Accepted: 2 November 1998 相似文献
6.
Methylene-H 4MPT reductase was found to be present in Archaeoglobus fulgidus in a specific activity of 1 U/mg. The reductase was purified 410-fold. The native enzyme showed an apparent molecular mass of approximately 200 kDa. Sodium dodecylsulfate/polyacrylamide gel electrophoresis revealed the presence of only 1 polypeptide of apparent molecular mass 35 kDa. The ultraviolet/visible spectrum of the reductase was almost identical to that of albumin indicating the absence of a chromophoric prosthetic group. The reductase was dependent on reduced coenzyme F 420 as electron donor. Neither NADH, NADPH, nor reduced viologen dyes could substitute for the reduced deazaflavin. From reciprocal plots, which showed an intersecting patter, a K
m for methylene-H 4MPT of 16 M, a K
m for F 420H 2 of 4 M, and a V
max of 450 U/mg (K cat=265 s -1) were obtained. The enzyme was found to be rapidly inactivated when incubated at 80°C in 100 mM Tris/HCl pH 7. The rate of inactivation, however, decreased to essentially zero in the presence of either F 420 (0.2 mM), methylene-H 4MPT (0.2 mM), albumin (1 mg/ml), or KCl (0.5 M). The N-terminal amino acid sequence was determined and found to be similar to that of methylene-H 4MPT reductase (F 420-dependent) from the methanogens Methanobacterium thermoautotrophicum, Methanosarcina barkeri, and Methanopyrus kandleri. The purification and some properties of formylmethanofuran dehydrogenase from A. fulgidus are also described.Abbreviations H 4MPT
tetrahydromethanopterin
- CH 2=H 4MPT
N
5, N
10-methylene-H 4MPT
- CH 3–H 4MPT
N
5-methyl-H 4MPT
- CHH 4MPT
methenyl-H 4MPT
- F 420
coenzyme F 420
- MFR
methanofuran
- CHO-MFR
formyl-MFR
- 1 U
1 mol/min 相似文献
7.
Methanopyrus kandleri belongs to a novel group of abyssal methanogenic archaebacteria that can grow at 110°C on H 2 and CO 2 and that shows no close phylogenetic relationship to any methanogen known so far. Methyl-coenzyme M reductase, the enzyme catalyzing the methane forming step in the energy metabolism of methanogens, was purified from this hyperthermophile. The yellow protein with an absorption maximum at 425 nm was found to be similar to the methyl-coenzyme M reductase from other methanogenic bacteria in that it was composed each of two -, - and -subunits and that it contained the nickel porphinoid coenzyme F 430 as prosthetic group. The purified reductase was inactive. The N-terminal amino acid sequence of the -subunit was determined. A comparison with the N-terminal sequences of the -subunit of methyl-coenzyme M reductases from other methanogenic bacteria revealed a high degree of similarity.Besides methyl-coenzyme M reductase cell extracts of M. kandleri were shown to contain the following enzyme activities involved in methanogenesis from CO 2 (apparent V max at 65°C): formylmethanofuran dehydrogenase, 0.3 U/mg protein; formyl-methanofuran: tetrahydromethanopterin formyltransferase, 13 U/mg; N
5,N 10-methenyltetrahydromethanopterin cyclohydrolase, 14 U/mg; N
5,N 10-methylenetetrahydromethanopterin dehydrogenase (H 2-forming), 33 U/mg; N
5,N 10-methylenetetrahydromethanopterin reductase (coenzyme F 420 dependent), 4 U/mg; heterodisulfide reductase, 2 U/mg; coenzyme F 420-reducing hydrogenase, 0.01 U/mg; and methylviologen-reducing hydrogenase, 2.5 U/mg. Apparent K m values for these enzymes and the effect of salts on their activities were determined.The coenzyme F 420 present in M. kandleri was identified as coenzyme F 420-2 with 2 -glutamyl residues.Abbreviations H–S-CoM
coenzyme M
- CH 3–S-CoM
methylcoenzyme M
- H–S-HTP
7-mercaptoheptanoylthreonine phosphate
- MFR
methanofuran
- CHO-MFR
formyl-MFR
- H 4MPT
tetrahydromethanopterin
- CHO–H 4MPT
N
5-formyl-H 4MPT
- CH=H 4MPT +
N
5,N 10-methenyl-H 4MPT
- CH 2=H 4MPT
N
5,N 10-methylene-H 4MPT
- CH 3–H 4MPT
N
5-methyl-H 4MPT
- F 420
coenzyme F 420
- 1 U=
1 mol/min 相似文献
8.
The sulfate-reducing Archaeoglobus fulgidus contains a number of enzymes previously thought to be unique for methanogenic Archaea. The purification and properties of two of these enzymes, of formylmethanofuran: tetrahydromethanopterin formyltransferase and of N
5, N
10-methylenetetrahydromethanopterin dehydrogenase (coenzyme F 420 dependent) are described here. A comparison of the N-terminal amino acid sequences and of other molecular properties with those of the respective enzymes from three methanogenic Archaea revealed a high degree of similarity.Abbreviations H 4MPT
tetrahydromethanopterin
- F 420
coenzyme
- F 420
formyltransferase, formylmethanofuran: tetrahydromethanopterin formyltransferase
- methylene-H 4MPT dehydrogenase
N
5, N
10-methylenetetrahydromethanopterin dehydrogenase
- methylene-H 4MPT recductase
N
5, N
10-methylenetetrahydromethanopterin reductase
- cyclohydrolase
N
5, N
10-methenyltetrahydromethanopterin cyclohydrolase
- APS
adenosine 5-phosphosulfate
- MOPS
3-(N-morpholino) propane sulfonic acid
- TRICINE
N-tris(hydroxymethyl)methylglycine
- MES
morpholinoethanesulfonic acid
- 1 U
1 mol/min 相似文献
9.
The strictly anaerobic Archaeon Ferroglobus placidus was grown chemolithoautotrophically on H 2 and nitrate and analyzed for enzymes and coenzymes possibly involved in autotrophic CO 2 fixation. The following enzymes were found [values in parentheses = μmol min –1 (mg protein) –1]: formylmethanofuran dehydrogenase (0.2), formylmethanofuran:tetrahydromethanopterin formyltransferase (0.6), methenyltetrahydromethanopterin
cyclohydrolase (10), F 420-dependent methylenetetrahydromethanopterin dehydrogenase (1.5), F 420-dependent methylenetetrahydromethanopterin reductase (0.4), and carbon monoxide dehydrogenase (0.1). The cells contained
coenzyme F 420 (0.4 nmol/mg protein), tetrahydromethanopterin (0.9 nmol/ mg protein), and cytochrome b (4 nmol/mg membrane protein). From the enzyme and coenzyme composition of the cells, we deduced that autotrophic CO 2 fixation in F. placidus proceeds via the carbon monoxide dehydrogenase pathway as in autotrophically growing Archaeoglobus and Methanoarchaea species. Evidence is also presented that cell extracts of F. placidus catalyze the reduction of two molecules of nitrite to 1 N 2O with NO as intermediate (0.1 μmol N 2O formed per min and mg protein), showing that – at least in principle – F. placidus has a denitrifying capacity.
Received: 23 August 1996 / Accepted: 6 November 1996 相似文献
10.
Archaeoglobus fulgidus, a sulfate-reducing Archaeon with a growth temperature optimum of 83°C, uses the 5-deazaflavin coenzyme F 420 rather than pyridine nucleotides in catabolic redox processes. The organism does, however, require reduced pyridine nuclcotides for biosynthetic purposes. We describe here that the Archaeon contains a coenzyme F 420-dependent NADP reductase which links anabolism to catabolism. The highly thermostable enzyme was purfied 3600-fold by affinity chromatography to apparent homogeneity in a 60% yield. The native enzyme with an apparent molecular mass of 55 kDa was composed of only one type of subunit of apparent molecular mass of 28 kDa. Spectroscopic analysis of the enzyme did not reveal the presence of any chromophoric prosthetic group. The purified enzyme catalyzed the reversible reduction of NADP (apparent K
M 40 M) with reduced F 420 (apparent K
M 20M) with a specific activity of 660 U/mg (apparent V
max) at pH 8.0 (pH optimum) and 80°C (temperature optimum). It was specific for both coenzyme F 420 and NADP. Sterochemical investigations showed that the F 420-dependent NADP reductase was Si face specific with respect to C5 of F 420 and Si face specific with respect to C4 of NADP.Abbreviations F 420
coenzyme F 420
- F 420H 2
1,5-dihydrocoenzyme F 420
- H 4MPT
tetrahydromethanopterin
- CH=H 4MPT
N 5, N 10-methylenetetrahydromethanopterin
- MFR
methanofuran
- HPLC
high performance liquid chromatography
- methylene-H 4MPT dehydrogenase
N 5, N 10-methylenetetrahydromethanopterin dehydrogenase
- 1 U =
1 mol/min 相似文献
12.
Sulfate‐reducing methanotrophy by anaerobic methanotrophic archaea (ANME) and sulfate‐reducing bacteria (SRB) is a major biological sink of methane in anoxic methane‐enriched marine sediments. The physiology of a microbial community dominated by free‐living ANME‐1 at 14–16 cm below the seafloor in the G11 pockmark at Nyegga was investigated by integrated metagenomic and metaproteomic approaches. Total DNA was subjected to 454‐pyrosequencing (829 527 reads), and 16.6 Mbp of sequence information was assembled into 27352 contigs. Taxonomic analysis supported a high abundance of Euryarchaea (70%) with 66% of the assembled metagenome belonging to ANME‐1. Extracted sediment proteins were separated in two dimensions and subjected to mass spectrometry (LTQ‐Orbitrap XL). Of 356 identified proteins, 245 were expressed by ANME‐1. These included proteins for cold‐adaptation and production of gas vesicles, reflecting both the adaptation of the ANME‐1 community to a permanently cold environment and its potential for positioning in specific sediment depths respectively. In addition, key metabolic enzymes including the enzymes in the reverse methanogenesis pathway (except N 5,N 10‐methylene‐tetrahydromethanopterin reductase), heterodisulfide reductases and the F 420H 2:quinone oxidoreductase (Fqo) complex were identified. A complete dissimilatory sulfate reduction pathway was expressed by sulfate‐reducing Deltaproteobacteria. Interestingly, an APS‐reductase comprising Gram‐positive SRB and related sequences were identified in the proteome. Overall, the results demonstrated that our approach was effective in assessing in situ metabolic processes in cold seep sediments. 相似文献
13.
A hydrophobic, redox-active component with a molecular mass of 538 Da was isolated from lyophilized membranes of Methanosarcina mazei Gö1 by extraction with isooctane. After purification on a high-performance liquid chromatography column, the chemical structure was analyzed by mass spectroscopy and nuclear magnetic resonance studies. The component was called methanophenazine and represents a 2-hydroxyphenazine derivative which is connected via an ether bridge to a polyisoprenoid side chain. Since methanophenazine was almost insoluble in aqueous buffers, water-soluble phenazine derivatives were tested for their ability to interact with membrane-bound enzymes involved in electron transport and energy conservation. The purified F 420H 2 dehydrogenase from M. mazei Gö1 showed highest activity with 2-hydroxyphenazine and 2-bromophenazine as electron acceptors when F 420H 2 was added. Phenazine-1-carboxylic acid and phenazine proved to be less effective. The Km values for 2-hydroxyphenazine and phenazine were 35 and 250 μM, respectively. 2-Hydroxyphenazine was also reduced by molecular hydrogen catalyzed by an F 420-nonreactive hydrogenase which is present in washed membrane preparations. Furthermore, the membrane-bound heterodisulfide reductase was able to use reduced 2-hydroxyphenazine as an electron donor for the reduction of CoB-S-S-CoM. Considering all these results, it is reasonable to assume that methanophenazine plays an important role in vivo in membrane-bound electron transport of M. mazei Gö1. 相似文献
14.
Cell suspensions of Methanobrevibacter arboriphilus catalyzed the reduction of O 2 with H 2 at a maximal specific rate of 0.4 U (mol/min) per mg protein with an apparent K
m for O 2 of 30 M. The reaction was not inhibited by cyanide. The oxidase activity was traced back to a coenzyme F 420-dependent enzyme that was purified to apparent homogeneity and that catalyzed the oxidation of 2 F 420H 2 with 1 O 2 to 2 F 420 and 2 H 2O. The apparent K
m for F 420 was 30 M and that for O 2 was 2 M with a V
max of 240 U/mg at 37°C and pH 7.6, the pH optimum of the oxidase. The enzyme did not use NADH or NADPH as electron donor or H 2O 2 as electron acceptor and was not inhibited by cyanide. The 45-kDa protein, whose gene was cloned and sequenced, contained 1 FMN per mol and harbored a binuclear iron center as indicated by the sequence motif H–X– E–X– D–X 62– H–X 18– D–X 60– H. Sequence comparisons revealed that the F 420H 2 oxidase from M. arboriphilus is phylogenetically closely related to FprA from Methanothermobacter marburgensis (71% sequence identity), a 45-kDa flavoprotein of hitherto unknown function, and to A-type flavoproteins from bacteria (30–40%), which all have dioxygen reductase activity. With heterologously produced FprA from M. marburgensis it is shown that this protein is also a highly efficient F 420H 2 oxidase and that it contains 1 FMN and 2 iron atoms. The presence of F 420H 2 oxidase in methanogenic archaea may explain why some methanogens, e.g., the Methanobrevibacter species in the termite hindgut, cannot only tolerate but thrive under microoxic conditions.Dedicated to Hans Schlegel on the occasion of his 80th birthday. 相似文献
15.
Acetate-grown cells of Methanosarcina barkeri MS were found to form methane from H 2:CO 2 at the same rate as hydrogen-grown cells. Cells grown on acetate had similar levels of soluble F 420-reactive hydrogenase I, and higher levels of cytochrome-linked hydrogenase II compared to hydrogen-grown cells. The hydrogenase I and II activities in the crude extract of acetate-grown cells were separated by differential binding properties to an immobilized Cu 2+ column. Hydrogenase II did not react with ferredoxin or F 420, whereas hydrogenase I coupled to both ferredoxin and F 420. A reconstituted soluble protein system composed of purified CO dehydrogenase, F 420-reactive hydrogenase I fraction, and ferredoxin produced H 2 from CO oxidation at a rate of 2.5 nmol/min · mg protein. Membrane-bound hydrogenase II coupled H 2 consumption to the reduction of CoM-S-S-HTP and the synthesis of ATP. The differential function of hydrogenase I and II is ascribed to ferredoxin-linked hydrogen production from CO and cytochrome b-linked H 2 consumption coupled to methanogenesis and ATP synthesis, respectively. 相似文献
16.
Summary In most methanogenic archaea, two hydrogenase systems that can catalyze the reduction of coenzyme F 420 (F 420) with H 2 are present: (1) the F 420-reducing hydrogenase, which is a nickel iron-sulfur flavoprotein composed of three different subunits, and (2) the N
5, N 10-methylenetetrahydromethanopterin dehydrogenase system, which is composed of H 2-forming methylenetetrahydromethanopterin dehydrogenase and F 420-dependent methylenetetrahydromethanopterin dehydrogenase, both metal-free proteins without an apparent prosthetic group.
We report here that in nickel-limited chemostat cultures of Methanobacterium thermoautotrophicum, the specific activity of the F 420-reducing Ni/Fe-hydrogenase was essentially zero, whereas that of the H 2-forming methylenetetrahydromethanopterin dehydrogenase was six times higher, and that of the F 420-dependent methylenetetrahydromethanopterin dehydrogenase was four times higher than in cells grown under non-nickel-limited
conditions. This evidence supports the hypothesis that when M. thermoautotrophicum grows under conditions of nickel limitation, the reduction of F 420 with H 2 is catalyzed by the metal-free methylenetetrahydromethanopterin dehydrogenase system.
Received: 9 September 1997 / Accepted: 30 October 1997 相似文献
17.
F 420 is a unique cofactor present in a restricted range of microorganisms, including mycobacteria. It has been proposed that F 420 has an important role in the oxidoreductive reactions of Mycobacterium tuberculosis, possibly associated with anaerobic survival and persistence. The protein encoded by Rv0132c has a predicted N–terminal signal sequence and is annotated as an F 420–dependent glucose-6-phosphate dehydrogenase. Here we show that Rv0132c protein does not have the annotated activity. It does, however, co–purify with F 420 during expression experiments in M. smegmatis. We also show that the Rv0132c–F 420 complex is a substrate for the Tat pathway, which mediates translocation of the complex across the cytoplasmic membrane, where Rv0132c is anchored to the cell envelope. This is the first report of any F 420–binding protein being a substrate for the Tat pathway and of the presence of F 420 outside of the cytosol in any F 420–producing microorganism. The Rv0132c protein and its Tat export sequence are essentially invariant in the Mycobacterium tuberculosis complex. Taken together, these results show that current understanding of F 420 biology in mycobacteria should be expanded to include activities occurring in the extra-cytoplasmic cell envelope. 相似文献
18.
Coenzyme F 420 is involved in bioprocesses such as biosynthesis of antibiotics by streptomycetes, prodrug activation in Mycobacterium tuberculosis, and methanogenesis in archaea. F 420-dependent enzymes also attract interest as biocatalysts in organic chemistry. However, as only low F 420 levels are produced in microorganisms, F 420 availability is a serious bottleneck for research and application. Recent advances in our understanding of the F 420 biosynthesis enabled heterologous overproduction of F 420 in Escherichia coli, but the yields remained moderate. To address this issue, we rationally designed a synthetic operon for F 420 biosynthesis in E. coli. However, it still led to the production of low amounts of F 420 and undesired side-products. In order to strongly improve yield and purity, a screening approach was chosen to interrogate the gene expression-space of a combinatorial library based on diversified promotors and ribosome binding sites. The whole pathway was encoded by a two-operon construct. The first module (“core”) addressed parts of the riboflavin biosynthesis pathway and F O synthase for the conversion of GTP to the stable F 420 intermediate F O. The enzymes of the second module (“decoration”) were chosen to turn F O into F 420. The final construct included variations of T7 promoter strengths and ribosome binding site activity to vary the expression ratio for the eight genes involved in the pathway. Fluorescence-activated cell sorting was used to isolate clones of this library displaying strong F 420-derived fluorescence. This approach yielded the highest titer of coenzyme F 420 produced in the widely used organism E. coli so far. Production in standard LB medium offers a highly effective and simple production process that will facilitate basic research into unexplored F 420-dependent bioprocesses as well as applications of F 420-dependent enzymes in biocatalysis. 相似文献
19.
F 430 is the prosthetic group of the methylcoenzyme M reductase of methanogenic bacteria. The compound isolated from Methanosarcina barkeri appears to be identical to the one obtained from the only distinctly related Methanobacterium thermoautotrophicum. F 430 is thermolabile and in the presence of acetonitrile or C10
in4
sup-
two epimerization products are obtained upon heating; in the absence of these compounds F 430 is oxidized to 12, 13-didehydro-F 430. The latter is stereoselectively reduced under H 2 atmosphere to F 430 by cell-free extracts of M. barkeri or M. thermoautotrophicum. H 2 may be replaced by the reduced methanogenic electron carrier coenzyme F 420.Abbreviations CH 3S-CoM
methylcoenzyme M, 2-methylthioethanesulfonic acid
- HS-CoM
coenzyme M, 2-mercaptoethanesulfonic acid
- F 430
Ni(II) tetrahydro-(12, 13)-corphin with a uroporphinoid (III) ligand skeleton
- 13-epi-F 430 and 12,13-di-epi-F 430
the 12, 13- and 12, 13-derivatives of F 430
- 12, 13-didehydro-F 430
F 430 oxidized at C-12 and C-13
- coenzyme F 420
7,8-didemethyl-8-hydroxy-5-deazaflavin derivative
- coenzyme F 420H 2
reduced coenzyme F 420
- MV +
methylviologen semiquinone
- HPLC
high-performance liquid chromatography 相似文献
20.
Summary A sulfonated polysulfone membrane reactor was used for in situ regeneration and retention of coenzymes NADP (H) using the xylose reductase of Candida pelliculosa coupled with oxidoreductase system of Methanobacterium sp. in the reduction of xylose to xylitol with hydrogen gas. The membrane could almost completely reject the permeation of NADP (H) (92 and 97%), F 420 (97%) and the required enzymes (100%), but not reject for the permeation of xylitol (product). After 4-h reaction for the production of xylitol from xylose (93% yield), although 25% NADP (H) initially added was lost its activity due to unavoidable degradation, the membrane could reject the permeation of the remaining NADP (H) and F 420 at the level of 90 and 95%, respectively. 相似文献
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