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1.
Formaldehyde activating enzyme (Fae) was first discovered in methylotrophic bacteria, where it is involved in the oxidation
of methanol to CO 2 and in formaldehyde detoxification. The 18 kDa protein catalyzes the condensation of formaldehyde with tetrahydromethanopterin
(H 4MPT) to methylene-H 4MPT. We describe here that Fae is also present and functional in the methanogenic archaeon Methanosarcina barkeri. The faeA homologue in the genome of M. barkeri was heterologously expressed in Escherichia coli and the overproduced purified protein shown to actively catalyze the condensation reaction: apparent V
max=13 U/mg protein (1 U=μmol/min); apparent Km for H 4MPT=30 μM; apparent Km for formaldehyde=0.1 mM. By Western blot analysis the concentration of Fae in cell extracts of M. barkeri was determined to be in the order of 0.1% of the soluble cell proteins. Besides the faeA gene the genome of M. barkeri harbors a second gene, faeB-hpsB, which is shown to code for a 42 kDa protein with both Fae activity (3.6 U/mg) and hexulose-6-phosphate synthase (Hps) activity
(4.4 U/mg). The results support the recent proposal that in methanogenic archaea Fae and Hps could have a function in ribose
phosphate synthesis. 相似文献
2.
AbstractIn this study, the effects of Aspergillus niger in coculture with the basidiomycetes, Trametes versicolor, T. maxima, and Ganoderma spp., were studied to assess H 2O 2 production and laccase (Lac), Lignin Peroxidase (LiP), and manganese peroxidase (MnP) activities. The results indicated that maximum discoloration was of 97%, in the T. maxima and A. niger coculture, where the concentration of H 2O 2 was 5?mg/L and 6.3?mg/L in cultures without and with dye, respectively. These concentrations of H 2O 2 were 1.6- and 1.8-fold higher than monocultures of T. maxima (3.37?mg/L) and A. niger (3.87?mg/L), respectively. In the same coculture, the LiP and MnP enzyme activities also increased 12-fold, (from 0.08?U/mg to 0.99?U/mg), and 67-fold, (from 0.11?U/mg to 7.4?U/mg), respectively. The Lac activity increased 1.7-fold (from 13.46?U/mg to 24?U/mg). Further, a Box–Behnken experimental design indicated a 1.8-fold increase of MnP activity (from 7.4?U/mg to 13.3?U/mg). In addition, dye discoloration regression model obtained from the Box–Behnken experimental design showed a positively correlation with H 2O 2, ( R2?=?0.58) and a negatively correlation with Lac activity ( R2 = –0.7). 相似文献
3.
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
4.
The H 2 uptake activity (units/mg protein) of Clostridium pasteurianum cells with methylene blue as the electron acceptor increases with cell density independent of the growth conditions. The H 2 evolution activity (units/mg protein) of the same cells with reduced methyl viologen as the electron donor remains fairly constant under all growth conditions tested. Cells grown under N 2-fixing conditions have the highest H 2 uptake activity and were used for the purification of hydrogenase II (uptake hydrogenase). Attempts to separate hydrogenase II from hydrogenase I (bidirectional hydrogenase) by a previously published method were unreliable. We report here a new large-scale purification procedure which employs a rapid membrane filtration system to fractionate cell-free extracts. Hydrogenases I and II were easily filtered into the low-molecular-weight fraction ( Mr less than 100 000), and from this, hydrogenase II was further purified to a homogeneous state. Hydrogenase II is a monomeric iron-sulfur protein of molecular weight 53 000 containing eight iron atoms and eight acid-labile sulfur atoms per molecule. Hydrogenase II catalyzes both H 2 oxidation and H 2 evolution at rates of 3000 and 5.9 μmol H 2 consumed or evolved/min per mg protein, respectively. The purification procedure for hydrogenase II using the filtration system described greatly facilitates the large-scale purification of hydrogenase I and other enzymes from cell-free extracts of C. pasteurianum. 相似文献
5.
研究外源GA 3对盐胁迫下黄瓜种子萌发和幼苗生长的影响。结果表明,添加不同质量浓度GA 3的各处理,其发芽率、发芽势和发芽指数均显著高于NaCl胁迫处理,其中以100 mg/L GA 3处理的发芽势、发芽率和发芽指数最高,幼苗的叶面积、根长、根冠比也最大,同时叶片中叶绿素含量最高,幼苗叶片的光合速率( Pn)、气孔导度( Gs)、胞间CO 2摩尔分数( Ci)及蒸腾速率( Tr)等均达到最大;而当赤霉素的质量浓度为50 mg/L时,叶片中的POD活性为2 005 U/(g·min),达最大值。 相似文献
6.
Archaeoglobus fulgidus is an extremely thermophilic archaebacterium that can grow at the expense of lactate oxidation with sulfate to CO 2 and H 2S. The organism contains coenzyme F 420, tetrahydromethanopterin, and methanofuran which are coenzymes previously thought to be unique for methanogenic bacteria. We report here that the bacterium contains methylenetetrahydromethanopterin: F 420 oxidoreductase (20 U/mg), methenyltetrahydromethanopterin cyclohydrolase (0.9 U/mg), formyltetrahydromethanopterin: methanofuran formyltransferase (4.4 U/mg), and formylmethanofuran: benzyl viologen oxidoreductase (35 mU/mg). Besides these enzymes carbon monoxide: methyl viologen oxidoreductase (5 U/mg), pyruvate: methyl viologen oxidoreductase (0.7 U/mg), and membranebound lactate: dimethylnaphthoquinone oxidoreductase (0.1 U/mg) were found. 2-Oxoglutarate dehydrogenase, which is a key enzyme of the citric acid cycle, was not detectable. From the enzyme outfit it is concluded that in A. fulgidus lactate is oxidized to CO 2 via a modified acetyl-CoA/carbon monoxide dehydrogenase pathway involving C 1-intermediates otherwise only used by methanogenic bacteria.Non-standard abbreviations APS
adenosine 5-phosphosulfate
- BV
benzyl viologen
- DCPIP
2,6-dichlorophenolindophenol
- DMN
2,3-dimethyl-1,4-naphthoquinone
- DTT
DL-1,4-dithiothreitol
- H 4F
tetrahydrofolate
- H 4MPT
tetrahydromethanopterin
- CH 2
H 4MPT, methylene-H 4MPT
- CH
H 4MPT, methenyl-H 4MPT
- Mes
morpholinoethane sulfonic acid
- MFR
methanofuran
- Mops
morpholinopropane sulfonic acid
- MV
methyl viologen
- Tricine
N-tris(hydroxymethyl)-methylglycine
- U
mol product formed per min 相似文献
7.
Membranes and PS II particles retaining high rates of O 2-evolving activity have been isolated from the transformable cyanobacterium, Synechocystis sp. PCC6803. Membranes from cells grown under red light exhibit rates of O 2-evolution ranging from 500–700 mole O 2/mg chl/h. PS II particles are prepared by a simple procedure involving DEAE column chromatography of detergent extracts obtained by simultaneous treatment of membranes with octylglucoside and dodecylmaltoside. The isolated PS II fraction is enriched in polypeptides immunologically cross-reactive with polypeptides present in core reaction center preparations of spinach, exhibits 77 K fluorescence emission maxima at 685 and 696 nm, but not emission and absorption due to phycobilines and is capable of rates of O 2-evolution exceeding 1000 mole O 2/mg chl/h.Abbreviations DM
dodecyl--D-maltoside
- OG
octyl--D-glucoside 相似文献
8.
Exposure of Lemma sp. to SO 2 resulted in an increased activity of superoxide dismutase. About 3 to 4 fold increase in the activity was observed within 30 minutes after the plants were fumigated with 10 ml/l of SO 2. Paraquat, a well known superoxide generator, doubled the enzyme activity after 1 hour of treatment with 0.1 mM paraquat. Superoxide dismutase activity was also enhanced by cadmium treatment but the response was not immediate. Optimum increase in the activity of enzyme was observed after 4 days of treatment with 40 mg/l of cadmium in the medium. Treatment with H 2O 2 very clearly inhibited the activity of superoxide dismutase in Lemna. 相似文献
9.
6-Phosphogluconate dehydrogenase (6PG) was purified from rat small intestine with 36% yield and a specific activity of 15 U/mg.
On SDS/PAGE, one band with a mass of 52 kDa was found. On native PAGE three protein and two activity bands were observed.
The pH optimum was 7.35. Using Arrhenius plots, Ea, ΔH, Q10 and Tm for 6PGD were found to be 7.52 kcal/mol, 6.90 kcal/mol, 1.49 and 49.4°C, respectively. The enzyme obeyed “Rapid Equilibrium
Random Bi Bi” kinetic model with Km values of 595 ± 213 μ M for 6PG and 53.03±1.99 μ M for NADP. 1/ Vm versus 1/6PG and 1/NADP plots gave a Vm value of 8.91±1.92 U/mg protein. NADPH is the competitive inhibitor with a Ki of 31.91±1.31 μ M. The relatively small Ki for the 6PGD:NADPH complex indicates the importance of NADPH in the regulation of the pentose phosphate pathway through G6PD
and 6PGD. 相似文献
10.
We established an Na(2)S-free, large-scale overexpression system of deriving CODH II from thermophilic bacterium Carboxydothermus hydrogenoformans in Escherichia coli using a large-scale fermentor. Recombinant-CODH II showed a CO oxidation activity of 9,600 U/mg. In addition, recombinant-CODH II exhibited considerable CO(2) reduction activity, of 16.9 U/mg. 相似文献
11.
The generation and depletion of dissolved inorganic carbon (DIC) in a close-environment ureolytic biocalcification process by Bacillus pasteurii was evaluated. Three experimental sets, each containing 50 mM urea, were amended with either 50 mM Ca 2+ before incubation (set–I) or 100 mM Ca 2+ after 24-h incubation (set-II) or no Ca 2+ addition (urea control). Extent of ureolysis was maximum in urea control set (88%), followed by set–II (66.4%) and set–I (35.2%). Out of total DIC generated from microbial metabolism and ureolysis in set–I (277.6 mg/l) and set–II (464.9 mg/l), only about 54.1 mg/l and 180.1 mg/l was precipitated as CaCO3, whereas 189.3 mg/l and 231.3 mg/l DIC escaped into headspace, respectively. Increased time separation between ureolysis and calcification steps in set–II and higher dosage of Ca2+ resulted in synergistic improvement in DIC capture. In a reusability test, the spent supernatant from set–II could precipitate additional amount CaCO3from CO2saturated water,which was twice as much as that of the fresh media control. 相似文献
12.
The microbial production of dextranase using cheap carbon sources is beneficial to solve the economic loss caused by the accumulation of dextran in syrup. A food-grade microbial cell factory was constructed by introducing the dextranase encoding gene DEX from Chaetomium gracile to the chromosome of Bacillus subtilis, and the antibiotic resistance marker gene was subsequently deleted via the Cre/loxP strategy. The dual-promoter system with a sequentially arranged constitutive P43 promoter resulted in an 85 % increase in DEX expression. Under the optimal fermentation conditions of 10 g/L maltose, 15 g/L casein, 1 g/L Na 2HPO 4, 1 g/L FeSO 4 and 8 g/L NaCl, DEX activity was increased from 2.625 to 64.34 U/mL. Recombinant DEX was purified 5.98-fold with a recovery ratio of 26.67 % and specific activity of 3935.02 U/mg. Enzyme activity was optimal at 55 °C and pH 5.0 and remained 80.34 % and 71.36 % of the initial activity at 55 °C and pH 4.0 after 60 min, respectively. The enzyme possessed high activity in the presence of Co 2+, while Ag + showed the strongest inhibition ability. The optimal substrate was 20 g/L dextran T-2000. The findings could facilitate the low-cost, large-scale production of food-grade DEX for use in the sugar industry. 相似文献
13.
A new H 2O 2-generating pyranose oxidase was purified as a strong antifungal protein from an arbuscular mycorrhizal fungus, Tricholoma matsutake. The protein showed a molecular mass of 250 kDa in gel filtration, and probably consisted of four identical 62 kDa subunits. The protein contained flavin moiety and it oxidized D-glucose at position C-2. H 2O 2 and D-glucosone produced by the pyranose oxidase reaction showed antifungal activity, suggesting these compounds were the molecular basis of the antifungal property. The V max, K m, and k cat for D-glucose were calculated to be 26.6 U/mg protein, 1.28 m M, and 111/s, respectively. The enzyme was optimally active at pH 7.5 to 8.0 and at 50°C. The preferred substrate was D-glucose, but 1,5-anhydro- D-glucitol, L-sorbose, and D-xylose were also oxidized at a moderate level. The cDNA encodes a protein consisting of 564 amino acids, showing 35.1% identity to Coriolus versicolor pyranose oxidase. The recombinant protein was used for raising the antibody. 相似文献
14.
The anticonvulsant activity of bis(acetato)tetrakis(imidazole) copper(II), Cu(OAc) 2(Im) 4, was studied in normal mice using chemical convulsions induced by strychnine, thiosemicarbazide, picrotoxin, and pentelenetetrazol.
Intraperitoneal administration of Cu(OAc) 2(Im) 4, 50 mg/kg body mass, has delayed the onset of strychnine (3 mg/kg)-induced convulsion by 204% ( p≤0.005) and thiosemicarbazide (20 mg/kg)-induced convulsant by 61% ( p≤0.005). The changes in the onset of picrotoxin-(6 mg/kg) and pentelenetetrazol (50 mg/kg)-induced convulsions were not significant.
The same dosage of the copper compound was effective in delaying the lethal time and reducing the mortality rate of treated
animals. The anticonvulsant activity of Cu(OAc) 2(Im) 4 complex against strychnine was not related to its constituents because the inorganic form of copper such as copper chloride,
copper acetate, and the parent imidazole has no anticonvulsant activity. Other copper(II) complexes like copper(II)aspirinate
and bis(acetato)bis(2-methyl imidazole) copper(II) were less effective. 相似文献
15.
The hyperthermophilic anaerobic eubacterium Thermotoga maritima was grown on glucose as carbon and energy source. During growth 1 mol glucose was fermented to 2 mol acetate, 2 mol CO 2 and 4 mol H 2. The molar growth yicld on glucose (Y glucose) was about 45 g cell dry mass/mol glucose. In the presence of elemental sulfur growing cultures of T. maritima converted 1 mol glucose to 2 mol acetate, 2 mol CO 2 about 0.5 mol H 2 and about 3.5 mol H 2S. Y glucose was about 45 g/mol. Cell extracts contained all enzymes of the Embden-Meyerhof pathway: hexokinase (0.29 U/mg, 50°C), glucose-6-phosphate isomerase (0.56 U/mg, 50°C), phosphofructokinase (0.19 U/mg, 50° C), fructose-1,6-bisphosphate aldolase (0.033 U/mg, 50°C), triosephosphate isomerase (6.3 U/mg, 50°C), glyceraldehyde-3-phosphate dehydrogenase (NAD + reducing: 0.63 U/mg, 50°C), phosphoglycerate kinase (3.7 U/mg, 50°C), phosphoglycerate mutase (0.4 U/mg, 50°C); enolase (4 U/mg, 80°C), pyruvate kinase (0.05 U/mg, 50°C). Furthermore, cell extracts contained pyruvate: ferredoxin oxidoreductasee (0.43 U/mg, 60°C); NADH: ferredoxin oxidoreductase (benzylviologen reduction: 0.46 U/mg, 80°C); hydrogenase (benzylviologen reduction: 15 U/mg, 80°C), phosphate acetyltransferase (0.13 U/mg, 80°C), acetate kinase (1.2 U/mg, 55°C), lactate dehydrogenase (0.16 U/mg, 80°C) and pyruvate carboxylase (0.02 U/mg, 50°C). The findings indicate that the hyperthermophilic eubacterium T. maritima ferments sugars (glucose) to acetate, CO 2 and H 2 involving the Embden-Meyerhof pathway, phosphate acetyltransferase and acetate kinase. Thus, the organism differs from the hyperthermophilic archaeon Pyrococcus furiosus which ferments sugars to acetate, CO 2 and H 2 involving a modified non-phosphorylated Entner-Doudoroff pathway and acetyl-CoA synthetase (ADP forming). 相似文献
16.
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
17.
近年来,二氧化钛纳米颗粒(TiO 2NPs)环境释放量不断增加,并通过多种途径进入湿地生态系统,不可避免地影响到湿地生态系统环境和功能。然而,关于TiO 2NPs对沼泽土壤反硝化作用和氧化亚氮(N 2O)排放的影响机及制尚不明确。选择典型沼泽土壤,通过室内培养实验研究土壤理化性质、反硝化酶活性、反硝化速率(DNR)和N 2O排放对不同剂量TiO 2NPs 0 mg/kg (CK)、10 mg/kg (A10)、100 mg/kg (A100)、1000 mg/kg (A1000)输入的响应,探讨TiO 2NPs输入对沼泽土壤反硝化作用和N 2O排放影响的内在机制。结果表明:不同剂量TiO 2NPs处理显著降低了土壤pH ( P<0.05),A10处理显著降低土壤总有机碳(TOC)含量( P<0.01),A1000处理显著降低硝态氮(NO 3--N)和亚硝态氮(NO 2--N)含量( P<0.05)。TiO 2NPs处理抑制硝酸盐还原酶(NAR)活性,促进一氧化氮还原酶(NOR)和氧化亚氮还原酶(NOS)活性( P<0.01),A1000处理先促进后抑制了亚硝酸盐还原酶(NIR)活性( P<0.05)。不同剂量TiO 2NPs处理抑制了土壤DNR,促进了N 2O排放,TiO 2NPs处理通过抑制NIR活性,降低土壤DNR,同时通过促进NOR活性,提高N 2O排放。综上,TiO 2NPs输入通过影响反硝化还原酶活性改变沼泽土壤反硝化过程,导致沼泽土壤N 2O排放增加,改变湿地氮的源、汇功能,影响全球气候变化。为TiO 2NPs输入的湿地环境风险评估研究提供理论基础。 相似文献
18.
Methanosarcina barkeri was recently shown to contain two cytoplasmic isoenzymes of methylcobalamin: coenzyme M methyltransferase (methyltransferase 2). Isoenzyme I predominated in methanol-grown cells and isoenzyme II in acetate-grown cells. It was therefore suggested that isoenzyme I functions in methanogenesis from methanol and isoenzyme II in methanogenesis from acetate. We report here that cells of M. barkeri grown on trimethylamine, H 2/CO 2, or acetate contain mainly isoenzyme II. These cells were found to have in common that they can catalyze the formation of methane from trimethylamine and H 2, whereas only acetate-grown cells can mediate the formation of methane from acetate. Methanol-grown cells, which contained only low concentrations of isoenzyme II, were unable to mediate the formation of methane from both trimethylamine and acetate. These and other results suggest that isoenzyme II (i) is employed for methane formation from trimethylamine rather than from acetate, (ii) is constitutively expressed rather than trimethylamine-induced, and (iii) is repressed by methanol. The constitutive expression of isoenzyme II in acetate-grown M. barkeri can explain its presence in these cells. The N-terminal amino acid sequences of isoenzyme I and isoenzyme II were analyzed and found to be only 55% similar.Abbreviations H-S-CoM
coenzyme M or 2-mercaptoethane-sulfonate
- CH 3-S-CoM
methyl-coenzyme M or 2(methylthio)-ethanesulfonate
- [Co]
cobalamin
- CH 3-[Co]
methylcobalamin
- H 4MPT
tetrahydromethanopterin
- CH 3-H 4MPT
N
5-methyltetrahydromethanopterin
- MT 1
methyltransferase 1 or methanol: 5-hydroxybenzimidazolyl cobamide methyltransferase
- MT 2
methyltransferase 2 or methylcobalamin: coenzyme M methyltransferase
- Mops
morpholinopropanesulfonate
- 1 U =
1 mol/min 相似文献
19.
Cell extracts of Methanosarcina barkeri grown on methanol in media supplemented with molybdate exhibited a specific activity of formylmethanofuran dehydrogenase of approximately 1 U (1 mol/min)/mg protein. When the growth medium was supplemented with tungstate rather than with molybdate, the specific activity was only 0.04 U/mg. Despite this reduction in specific activity growth on methanol was not inhibited. An inhibition of both growth and synthesis of active formylmethanofuran dehydrogenase was observed, however, when H 2 and CO 2 were the energy substrates. The results indicate that, in contrast to Methanobacterium wolfei and Methanobacterium thermoautotrophicum, M. barkeri possesses only a molybdenum containing formylmethanofuran dehydrogenase and not in addition a tungsten isoenzyme. 相似文献
20.
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
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