1
|
Kosem N, Honda Y, Watanabe M, Takagaki A, Tehrani ZP, Haydous F, Lippert T, Ishihara T. Photobiocatalytic H2 evolution of GaN:ZnO and [FeFe]-hydrogenase recombinant Escherichia coli. Catal Sci Technol 2020. [DOI: 10.1039/d0cy00128g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The need for sustainable, renewable and low-cost approaches is a driving force behind the development of solar-to-H2 conversion technologies.
Collapse
Affiliation(s)
- Nuttavut Kosem
- International Institute for Carbon-Neutral Energy Research (I2CNER)
- Kyushu University
- Fukuoka 819-0395
- Japan
- Department of Applied Chemistry
| | - Yuki Honda
- Department of Chemistry, Biology and Environmental Science
- Faculty of Science
- Nara Women's University
- Nara 630-8506
- Japan
| | - Motonori Watanabe
- International Institute for Carbon-Neutral Energy Research (I2CNER)
- Kyushu University
- Fukuoka 819-0395
- Japan
| | - Atsushi Takagaki
- International Institute for Carbon-Neutral Energy Research (I2CNER)
- Kyushu University
- Fukuoka 819-0395
- Japan
- Department of Applied Chemistry
| | - Zahra Pourmand Tehrani
- Laboratory for Multiscale Materials Experiments
- Paul Scherrer Institut
- CH-5232 Villigen PSI
- Switzerland
| | - Fatima Haydous
- Laboratory for Multiscale Materials Experiments
- Paul Scherrer Institut
- CH-5232 Villigen PSI
- Switzerland
- Division of Applied Physical Chemistry
| | - Thomas Lippert
- International Institute for Carbon-Neutral Energy Research (I2CNER)
- Kyushu University
- Fukuoka 819-0395
- Japan
- Laboratory for Multiscale Materials Experiments
| | - Tatsumi Ishihara
- International Institute for Carbon-Neutral Energy Research (I2CNER)
- Kyushu University
- Fukuoka 819-0395
- Japan
- Department of Applied Chemistry
| |
Collapse
|
2
|
Greene BL, Schut GJ, Adams MWW, Dyer RB. Pre-Steady-State Kinetics of Catalytic Intermediates of an [FeFe]-Hydrogenase. ACS Catal 2017. [DOI: 10.1021/acscatal.6b03276] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Brandon L. Greene
- Department
of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Gerrit J. Schut
- Department
of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, United States
| | - Michael W. W. Adams
- Department
of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, United States
| | - R. Brian Dyer
- Department
of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| |
Collapse
|
3
|
Sander K, Wilson CM, Rodriguez M, Klingeman DM, Rydzak T, Davison BH, Brown SD. Clostridium thermocellum DSM 1313 transcriptional responses to redox perturbation. BIOTECHNOLOGY FOR BIOFUELS 2015; 8:211. [PMID: 26692898 PMCID: PMC4676874 DOI: 10.1186/s13068-015-0394-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 11/24/2015] [Indexed: 05/21/2023]
Abstract
BACKGROUND Clostridium thermocellum is a promising consolidated bioprocessing candidate organism capable of directly converting lignocellulosic biomass to ethanol. Current ethanol yields, productivities, and growth inhibitions are industrial deployment impediments for commodity fuel production by this bacterium. Redox imbalance under certain conditions and in engineered strains may contribute to incomplete substrate utilization and may direct fermentation products to undesirable overflow metabolites. Towards a better understanding of redox metabolism in C. thermocellum, we established continuous growth conditions and analyzed global gene expression during addition of two stress chemicals (methyl viologen and hydrogen peroxide) which changed the fermentation redox potential. RESULTS The addition of methyl viologen to C. thermocellum DSM 1313 chemostat cultures caused an increase in ethanol and lactate yields. A lower fermenter redox potential was observed in response to methyl viologen exposure, which correlated with a decrease in cell yield and significant differential expression of 123 genes (log2 > 1.5 or log2 < -1.5, with a 5 % false discovery rate). Expression levels decreased in four main redox-active systems during methyl viologen exposure; the [NiFe] hydrogenase, sulfate transport and metabolism, ammonia assimilation (GS-GOGAT), and porphyrin/siroheme biosynthesis. Genes encoding sulfate transport and reduction and porphyrin/siroheme biosynthesis are co-located immediately downstream of a putative iscR regulatory gene, which may be a cis-regulatory element controlling expression of these genes. Other genes showing differential expression during methyl viologen exposure included transporters and transposases. CONCLUSIONS The differential expression results from this study support a role for C. thermocellum genes for sulfate transport/reduction, glutamate synthase-glutamine synthetase (the GS-GOGAT system), and porphyrin biosynthesis being involved in redox metabolism and homeostasis. This global profiling study provides gene targets for future studies to elucidate the relative contributions of prospective pathways for co-factor pool re-oxidation and C. thermocellum redox homeostasis.
Collapse
Affiliation(s)
- Kyle Sander
- />Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, TN 37996 USA
- />BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996 USA
| | - Charlotte M. Wilson
- />BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Miguel Rodriguez
- />BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Dawn M. Klingeman
- />BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Thomas Rydzak
- />BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Brian H. Davison
- />Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, TN 37996 USA
- />BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Steven D. Brown
- />Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, TN 37996 USA
- />BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- />Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| |
Collapse
|
4
|
Orgill JJ, Chen C, Schirmer CR, Anderson JL, Lewis RS. Prediction of methyl viologen redox states for biological applications. Biochem Eng J 2015. [DOI: 10.1016/j.bej.2014.11.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
5
|
Yang H, Gandhi H, Shi L, Kreuzer HW, Ostrom NE, Hegg EL. Using gas chromatography/isotope ratio mass spectrometry to determine the fractionation factor for H2 production by hydrogenases. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2012; 26:61-68. [PMID: 22215579 DOI: 10.1002/rcm.5298] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Hydrogenases catalyze the reversible formation of H(2), and they are key enzymes in the biological cycling of H(2). H isotopes have the potential to be a very useful tool in quantifying hydrogen ion trafficking in biological H(2) production processes, but there are several obstacles that have thus far limited the application of this tool. Here, we describe a new method that overcomes some of these barriers and is specifically designed to measure isotopic fractionation during enzyme-catalyzed H(2) evolution. A key feature of this technique is that purified hydrogenases are employed, allowing precise control over the reaction conditions and therefore a high level of precision. In addition, a custom-designed high-throughput gas chromatograph/isotope ratio mass spectrometer is employed to measure the isotope ratio of the H(2). Using our new approach, we determined that the fractionation factor for H(2) production by the [NiFe]-hydrogenase from Desulfovibrio fructosovorans is 0.273 ± 0.006. This result indicates that, as expected, protons are highly favored over deuterium ions during H(2) evolution. Potential applications of this newly developed method are discussed.
Collapse
Affiliation(s)
- Hui Yang
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824-1319, USA
| | | | | | | | | | | |
Collapse
|
6
|
Dabrock B, Bahl H, Gottschalk G. Parameters Affecting Solvent Production by Clostridium pasteurianum. Appl Environ Microbiol 2010; 58:1233-9. [PMID: 16348691 PMCID: PMC195580 DOI: 10.1128/aem.58.4.1233-1239.1992] [Citation(s) in RCA: 286] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The effect of pH, growth rate, phosphate and iron limitation, carbon monoxide, and carbon source on product formation by Clostridium pasteurianum was determined. Under phosphate limitation, glucose was fermented almost exclusively to acetate and butyrate independently of the pH and growth rate. Iron limitation caused lactate production (38 mol/100 mol) from glucose in batch and continuous culture. At 15% (vol/vol) carbon monoxide in the atmosphere, glucose was fermented to ethanol (24 mol/100 mol), lactate (32 mol/100 mol), and butanol (36 mol/100 mol) in addition to the usual products, acetate (38 mol/100 mol) and butyrate (17 mol/100 mol). During glycerol fermentation, a completely different product pattern was found. In continuous culture under phosphate limitation, acetate and butyrate were produced only in trace amounts, whereas ethanol (30 mol/100 mol), butanol (18 mol/100 mol), and 1,3-propanediol (18 mol/100 mol) were the major products. Under iron limitation, the ratio of these products could be changed in favor of 1,3-propanediol (34 mol/100 mol). In addition, lactate was produced in significant amounts (25 mol/100 mol). The tolerance of C. pasteurianum to glycerol was remarkably high; growth was not inhibited by glycerol concentrations up to 17% (wt/vol). Increasing glycerol concentrations favored the production of 1,3-propanediol.
Collapse
Affiliation(s)
- B Dabrock
- Institut für Mikrobiologie, Grisebachstrasse 8, Georg-August-Universität Göttingen, W-3400 Göttingen, Federal Republic of Germany
| | | | | |
Collapse
|
7
|
Thomas CM, Liu T, Hall MB, Darensbourg MY. Series of Mixed Valent Fe(II)Fe(I) Complexes That Model the Hox State of [FeFe]Hydrogenase: Redox Properties, Density-Functional Theory Investigation, and Reactivities with Extrinsic CO. Inorg Chem 2008; 47:7009-24. [DOI: 10.1021/ic800654a] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Tianbiao Liu
- Department of Chemistry, Texas A&M University, College Station, Texas 77845
| | - Michael B. Hall
- Department of Chemistry, Texas A&M University, College Station, Texas 77845
| | | |
Collapse
|
8
|
SANEHIRA Y, UCHIDA S, KUBO T, SEGAWA H. A Distinguished Retentive Memory Using Polyethylene Glycol Electrolyte Solvent for Viologen Modified Titania Electrochromic Device. ELECTROCHEMISTRY 2008. [DOI: 10.5796/electrochemistry.76.150] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|
9
|
|
10
|
Llama MJ, Serra JL, Rao KK, Hall DO. Isolation of two hydrogenase activities in Chromatium. EUROPEAN JOURNAL OF BIOCHEMISTRY 2005; 114:89-96. [PMID: 7011805 DOI: 10.1111/j.1432-1033.1981.tb06176.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Kinetic, chromatographic and electrophoretic studies of Chromatium hydrogenase show the existence in vitro of two different activities (I and II). The two hydrogenases exhibit different kinetic parameters and properties. Using reduced methyl viologen, Km and [S]0.5 values of about 20 microM and 360 microM were calculated for the hydrogenases I and II, respectively. Hill plots revealed that hydrogenase I followed classical hyperbolic (Michaelis-Menten) kinetics. However, a Hill coefficient (h = 0.68) indicating non-hyperbolic kinetics could be shown for hydrogenase II. After several purification steps hydrogenase II still showed kinetics typical of the action of either (a) two enzymes each of which shows Michaelis-Menten kinetics but with different substrate affinities or (b) only one enzyme which shows apparent negative cooperative regulation. The molecular weights of the hydrogenases were about 37,000 (I) and 55,000 (II) when determined by gel filtration. Sodium dodecyl sulphate/polyacrylamide gel electrophoresis revealed that both enzymes give a coincidental single protein band with the same relative mobility indicating a molecular weight of 31,000. Both hydrogenases were able to catalyse the reversible activation of H2 in the presence of artificial electron carriers but with different rates, hydrogenase II being much more active in the H2-uptake mode. The kinetic properties and molecular weight of hydrogenase II are partially modified by high ionic strength resulting in an increased substrate affinity and Hill coefficient and thus resembling hydrogenase I. These results are interpreted as due to the existence in vitro of monomeric and dimeric forms of Chromatium hydrogenase.
Collapse
|
11
|
Hyman MR, Arp DJ. Acetylene is an active-site-directed, slow-binding, reversible inhibitor of Azotobacter vinelandii hydrogenase. Biochemistry 2002. [DOI: 10.1021/bi00394a023] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
12
|
Lemon BJ, Peters JW. Photochemistry at the Active Site of the Carbon Monoxide Inhibited Form of the Iron-Only Hydrogenase (CpI). J Am Chem Soc 2000. [DOI: 10.1021/ja9943703] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Brian J. Lemon
- Department of Chemistry and Biochemistry Utah State University, Logan, Utah 84322-0300
| | - John W. Peters
- Department of Chemistry and Biochemistry Utah State University, Logan, Utah 84322-0300
| |
Collapse
|
13
|
He SH, Woo SB, DerVartanian DV, Le Gall J, Peck HD. Effects of acetylene on hydrogenases from the sulfate reducing and methanogenic bacteria. Biochem Biophys Res Commun 1989; 161:127-33. [PMID: 2543405 DOI: 10.1016/0006-291x(89)91570-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The effect of acetylene on the activity of the three types of hydrogenase from the anaerobic sulfate reducing bacteria has been investigated. The (Fe) hydrogenase is resistant to inhibition by acetylene while the nickel-containing hydrogenases are inhibited by acetylene with the (NiFe) hydrogenase being 10-50 fold more sensitive than the (NiFeSe) hydrogenase. In addition the Ni(III) EPR signal (g approximately 2.3) of the "as isolated" (NiFe) hydrogenase was significantly decreased in intensity upon exposure to acetylene.
Collapse
Affiliation(s)
- S H He
- Department of Biochemistry, School of Chemical Sciences, University of Georgia, Athens 30602
| | | | | | | | | |
Collapse
|
14
|
Murrell SA, Lowery RG, Ludden PW. ADP-ribosylation of dinitrogenase reductase from Clostridium pasteurianum prevents its inhibition of nitrogenase from Azotobacter vinelandii. Biochem J 1988; 251:609-12. [PMID: 3135803 PMCID: PMC1149044 DOI: 10.1042/bj2510609] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The effect of ADP-ribosylation of dinitrogenase reductase on its binding to dinitrogenase was investigated. Dinitrogenase reductase from Clostridium pasteurianum (Cp2) was a substrate for the ADP-ribosyltransferase and the dinitrogenase-reductase-activating glycohydrolase from Rhodospirillum rubrum. ADP-ribosylation inactivated Cp2 and prevented its formation of a tight complex with dinitrogenase from Azotobacter vinelandii (Av1). The complex between Cp2 and Av1 could not be ADP-ribosylated once it formed.
Collapse
Affiliation(s)
- S A Murrell
- Department of Biochemistry, College of Agriculture and Life Sciences, University of Wisconsin, Madison 53706-1569
| | | | | |
Collapse
|
15
|
Church DL, Rabin HR, Laishley EJ. Role of hydrogenase 1 of Clostridium pasteurianum in the reduction of metronidazole. Biochem Pharmacol 1988; 37:1525-34. [PMID: 3282518 DOI: 10.1016/0006-2952(88)90014-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Competition studies between the phosphoroclastic reaction and the metronidazole reduction reaction using dialyzed crude cell-free extracts of Clostridium pasteurianum which were essentially devoid of Hydrogenase 1 activity demonstrated that this enzyme plays an important role in the reduction of metronidazole. To determine further the exact function for Hydrogenase 1 in the reduction of the drug, this enzyme was highly purified from C. pasteurianum. Metronidazole reduction activity copurified with Hydrogenase 1 specific activity throughout the purification procedure. Drug reduction required the presence of an electron carrier and could not be accomplished by the enzyme alone. Ferredoxin, and also the low potential electron carrier dyes, methyl and benzyl viologen, and the flavin coenzymes, FAD and flavin mononucleotide (FMN), could couple the reduction of metronidazole. Hydrogenase 1 activity and its metronidazole reduction activity were inactivated irreversibly in the presence of oxygen. Metronidazole could be reduced only by an electron carrier-Hydrogenase 1 mechanism or directly by sodium dithionite.
Collapse
Affiliation(s)
- D L Church
- Department of Microbiology and Infectious Diseases, University of Calgary, Alberta, Canada
| | | | | |
Collapse
|
16
|
O'Brian MR, Maier RJ. Hydrogen metabolism in Rhizobium: energetics, regulation, enzymology and genetics. Adv Microb Physiol 1988; 29:1-52. [PMID: 3132815 DOI: 10.1016/s0065-2911(08)60345-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- M R O'Brian
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218
| | | |
Collapse
|
17
|
Patil DS, Czechowski MH, Huynh BH, LeGall J, Peck HD, DerVartanian DV. A reversible effect of low carbon monoxide concentrations on the EPR spectra of the periplasmic hydrogenase from Desulfovibrio vulgaris. Biochem Biophys Res Commun 1986; 137:1086-93. [PMID: 3015136 DOI: 10.1016/0006-291x(86)90336-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effect of low concentrations of CO (0.93 - 5.58 microM) on the EPR spectrum of the periplasmic non-heme iron hydrogenase from D. vulgaris has been investigated. The "g = 2.06" EPR signal is maximally induced (0.94 spin/molecule) at 46.5 microM CO and partial induction of the EPR signal could be observed at 0.93 microM CO. This effect is reversed by removal of the CO or irradiation of the hydrogenase with white light.
Collapse
|
18
|
|
19
|
Dér A, Bagyinka C, Páli T, Kovács KL. Effect of enzyme concentration on apparent specific activity of hydrogenase. Anal Biochem 1985; 150:481-6. [PMID: 3911822 DOI: 10.1016/0003-2697(85)90538-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The effect of enzyme concentration on the H2-uptake and H2-evolving activities of the reversible hydrogenase from Thiocapsa roseopersicina was examined. In the activity range assayed by a spectrophotometric technique the apparent H2-uptake specific activity varied greatly with hydrogenase concentration. Study of H2-evolving activity measured by the H2 electrode method and compared with a gas chromatographic assay also indicated that specific activity was highly dependent on enzyme concentration. The results indicate that the widely applied hydrogenase assays give systematically erroneous specific activity values. These assays should be used only for relative measurements and the hydrogenase concentration in the reaction mixture should be kept constant. To make the data from various laboratories comparable the assay parameters should be standardized.
Collapse
|
20
|
|
21
|
Abstract
The effects of sample geometry and enzyme concentration on the H2-evolving activity of hydrogenase from Thiocapsa roseopersicina was measured. The specific activity increased linearly with increasing interface area between the liquid and the gas phase. Enzyme concentration was varied over four orders of magnitude and within this range the apparent specific activity depended on hydrogenase concentration. The experimental findings have been interpreted by a mathematical model involving competing H2 consumption reactions. The observed phenomena interfere with the widely used hydrogenase assay so that most of the previously published specific activity values are underestimated and should be corrected. The systematic error due to these hitherto unspecified parameters can easily exceed 10 000%; therefore, a thorough standardization of the assay procedure is necessary in order to make the data from various laboratories comparable.
Collapse
|
22
|
Chen JS, Blanchard DK. Purification and properties of the H2-oxidizing (uptake) hydrogenase of the N2-fixing anaerobe Clostridium pasteurianum W5. Biochem Biophys Res Commun 1984; 122:9-16. [PMID: 6331453 DOI: 10.1016/0006-291x(84)90431-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Clostridium pasteurianum has two distinct hydrogenases, the bidirectional hydrogenase and the H2-oxidizing (uptake) hydrogenase. The H2-oxidizing hydrogenase has been purified (up to 970-fold) to a specific activity of 17,600 mumol H2 oxidized/min X mg protein (5 mM methylene blue) or 3.5 mumol H2 produced/min X mg protein (1 mM methyl viologen). The uptake hydrogenase has a Mr of 53,000 (one polypeptide chain). Depending upon how protein was measured, the Fe and S = contents (gatom/mol) were 4.7 and 5.2 (by the dye-binding assay) or 7.2 and 8.0 (by the Lowry method). Both reduced and oxidized forms of the enzyme gave electron paramagnetic resonance signals. The activation energy for H2-production and H2-oxidation by the uptake hydrogenase was 59.1 and 31.2 kJ/mol, respectively. In the exponential phase of growth, the ratio of uptake hydrogenase/bidirectional hydrogenase in NH3-grown cells was much lower than that in N2-fixing cells.
Collapse
|
23
|
Adams MW, Mortenson LE. The physical and catalytic properties of hydrogenase II of Clostridium pasteurianum. A comparison with hydrogenase I. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)39835-6] [Citation(s) in RCA: 125] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
|
24
|
Pezacka E, Wood HG. The synthesis of acetyl-CoA by Clostridium thermoaceticum from carbon dioxide, hydrogen, coenzyme A and methyltetrahydrofolate. Arch Microbiol 1984; 137:63-9. [PMID: 6424623 DOI: 10.1007/bf00425809] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
It has been demonstrated that enzymes from Clostridium thermoaceticum catalyze the following reaction in which Fd is ferredoxin and CH3THF is methyltetrahydrofolate. (for formula see text). The system involves hydrogenase, CO dehydrogenase, a methyltransferase, a corrinoid enzyme and other unknown components. Hydrogenase catalyzes the reduction of ferredoxin by H2; CO dehydrogenase then uses the reduced ferredoxin to reduce CO2 to a one-carbon intermediate that combines with CoASH and with a methyl group originating from CH3THF to form acetyl-CoA. It is proposed that these reactions are part of the mechanism which enables certain acetogenic autotrophic bacteria to grow on CO2 and H2.
Collapse
|
25
|
Vignais PM, Henry MF, Berlier Y, Lespinat PA. Effect of pH on H-2H exchange, H2 production and H2 uptake, catalysed by the membrane-bound hydrogenase of Paracoccus denitrificans. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1982. [DOI: 10.1016/0005-2728(82)90195-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
26
|
Davis JC, Averill BA. Evidence for a spin-coupled binuclear iron unit at the active site of the purple acid phosphatase from beef spleen. Proc Natl Acad Sci U S A 1982; 79:4623-7. [PMID: 6289309 PMCID: PMC346727 DOI: 10.1073/pnas.79.15.4623] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The purple acid phosphatase from beef spleen, which contains two iron atoms per molecule, is EPR silent in its native (oxidized) purple form. Treatment with mild reducing agents results in conversion to a pink, enzymatically active form, which exhibits an unusual EPR signal centered at g approximately equal to 1.77; double integration of the EPR spectrum gives one spin per two iron atoms. A similar EPR spectrum is observed for enzyme reduced anaerobically by one electron, using sodium dithionite. Variable-temperature magnetic susceptibility measurements show that the oxidized and reduced proteins are both antiferromagnetically coupled systems, with S = 0 and 1/2 ground states, respectively. Replacement of one of the iron atoms by zinc produces an FeZn enzyme with full catalytic activity. The FeZn enzyme exhibits a highly temperature dependent g = 4.3 EPR signal, and magnetic susceptibility data are consistent with an S = 5/2 paramagnet. Treatment of the FeZn enzyme with phosphate, a competitive inhibitor, results in sharpening of the EPR spectrum; double integration at 77 K gives one spin per iron. These results strongly suggest the presence of a spin-coupled bimetallic unit at the active site of the enzyme.
Collapse
|
27
|
Drake HL. Demonstration of hydrogenase in extracts of the homoacetate-fermenting bacterium Clostridium thermoaceticum. J Bacteriol 1982; 150:702-9. [PMID: 7040339 PMCID: PMC216419 DOI: 10.1128/jb.150.2.702-709.1982] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Cell-free extracts of the homoacetate-fermenting bacterium Clostridium thermoaceticum were shown to catalyze the hydrogen-dependent reduction of various artificial electron acceptors. The activity of the hydrogenase was optimal at pH 8.5 to 9 and was extremely sensitive to aeration. EDTA did not significantly reduce the liability of the enzymic activity to oxidation (aeration). At 50 degrees C, when both methyl viologen and hydrogen were at saturating concentrations with respect to hydrogenase, the specific activity of cell-free extracts approximated 4 mumol of H2 oxidized per min per mg of protein; fourfold higher specific activities were obtained when benzyl viologen was utilized as an electron acceptor. Activity stains of polyacrylamide gels demonstrated the presence of a single hydrogenase band, suggesting that the catalytic activity in cell extracts was due to a single enzyme. The activity was stable for at least 32 min at 55 degrees C but was slowly inactivated at 70 degrees C. NAD, NADP, flavin adenine dinucleotide, flavin mononucleotide, and ferredoxin were not significantly reduced, but possible reduction of the particulate b-type cytochrome of C. thermoaceticum was observed. NaCl, sodium dodecyl sulfate, iodoacetamide, and CO were shown to inhibit catalysis. A kinetic study is presented, and the possible physiologic roles for hydrogenase in C. thermoaceticum ar discussed.
Collapse
|
28
|
Fernandez VM, Munilla R, Ballesteros A. Influence of the redox potential on the activity of Clostridium pasteurianum and Chromatium hydrogenases. Arch Biochem Biophys 1982; 215:129-35. [PMID: 7046637 DOI: 10.1016/0003-9861(82)90286-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
|
29
|
Fernández VM, Gutiérrez C, Ballesteros A. Determination of hydrogenase activity using an anaerobic spectrophotometric device. Anal Biochem 1982; 120:85-90. [PMID: 7046506 DOI: 10.1016/0003-2697(82)90320-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
|
30
|
|
31
|
Klibanov AM, Huber J. Application of immobilized hydrogenase for the detritiation of water. Biotechnol Bioeng 1981. [DOI: 10.1002/bit.260230713] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
32
|
Khan SM, Klibanov AM, Kaplan NO, Kamen MD. The effect of electron carriers and other ligands on oxygen stability of clostridial hydrogenase. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 659:457-65. [PMID: 7020766 DOI: 10.1016/0005-2744(81)90071-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The effects of various electron carriers, a substrate (H2) and a reversible inhibitor (CO) on the rate of irreversible oxygen inactivation of clostridial hydrogenase (ferredoxin: H+ oxidoreductase, EC 1.18.3.1) have been studied kinetically. Some electron carriers (e.g., clostridial ferredoxin and methyl viologen) greatly stabilize the enzyme, some (FAD, FMN) drastically reduce its stability, while others (benzyl viologen and methylene blue) only slightly alter the stability. Competitive experiments indicate that stabilizers and destabilizers do not compete with each other for binding with the active center of hydrogenase. Hydrogen and CO do not affect the rate of the oxygen inactivation. On the basis of the results obtained herein and kinetic data on hydrogenase catalysis from the literature, it is concluded that the active center of this hydrogenase comprises at least three different independent subsites. The first one (presumably an iron atom of the iron-sulfur cluster) binds H2 and CO and does not contribute to the oxygen stability. The second one binds stabilizers like methyl viologen while the third one binds destabilizers like FMN and FAD.
Collapse
|
33
|
Okura I, Nakamura K, Nakamura S. Kinetics of methyl viologen reduction by hydrogen catalyzed by hydrogenase from Desulfovibrio vulgaris. J Inorg Biochem 1981; 14:155-61. [PMID: 7252493 DOI: 10.1016/s0162-0134(00)80036-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
|
34
|
Houchins JP, Burris RH. Comparative characterization of two distinct hydrogenases from Anabaena sp. strain 7120. J Bacteriol 1981; 146:215-21. [PMID: 6783615 PMCID: PMC217072 DOI: 10.1128/jb.146.1.215-221.1981] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Two distinct hydrogenases, hereafter referred to as "uptake" and "reversible" hydrogenase, were extracted from Anabaena sp. strain 7120 and partially purified. The properties of the two enzymes were compared in cell-free extracts. Uptake hydrogenase was largely particulate, and although membrane bound, it could catalyze an oxyhydrogen reaction. Particulate and solubilized uptake hydrogenase could catalyze H2 uptake with a variety of artificial electron acceptors which had midpoint potentials above 0 mV. Reversible hydrogenase was soluble, could donate electrons rapidly to electron acceptors of both positive and negative midpoint potential, and could evolve H2 rapidly when provided with reduced methyl viologen. Uptake hydrogenase was irreversibly inactivated by O2, whereas reversible hydrogenase was reversibly inactivated and could be reactivated by exposure to dithionite or H2. Reversible hydrogenase was stable to heating at 70 degrees C, but uptake hydrogenase was inactivated with a half-life of 12 min at this temperature. Uptake hydrogenase was eluted from Sephadex G-200 in a single peak of molecular weight 56,000, whereas reversible hydrogenase was eluted in two peaks with molecular weights of 165,000 and 113,000. CO was competitive with H2 for each enzyme; the Ki's for CO were 0.0095 atm for reversible hydrogenase and 0.039 atm for uptake hydrogenase. The pH optima for H2 evolution and H2 uptake by reversible hydrogenase were 6 and 9, respectively. Uptake hydrogenase existed in two forms with pH optima of 6 and 8.5. Both enzymes had very low Km's for H2, and neither was inhibited by C2H2.
Collapse
|
35
|
van Dijk C, Veeger C. The effects of pH and redox potential on the hydrogen production activity of the hydrogenase from Megasphaera elsdenii. EUROPEAN JOURNAL OF BIOCHEMISTRY 1981; 114:209-19. [PMID: 7011807 DOI: 10.1111/j.1432-1033.1981.tb05138.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The effects of temperature on the ionization constant (pK') and apparent midpoint potential (EB) of the unprotonated species of Megasphaera elsdenii flavodoxin hydroquinone shows that, above 15 degrees C, delta pK' . K-1 = -9.7 X 10(-3) and delta EB . K-1 = -0.6 mV. The effects of pH and redox potential on the hydrogen production activity with fixed concentrations of methyl viologen semiquinone (0.3 mM; artificial donor) and M. elsdenii flavodoxin hydroquinone (50 microM; natural donor) show that with decreasing pH the activity increases. Irrespective of the pH and electron donor, at increasing redox potential, a redox-potential-independent production activity is followed by a redox-potential-dependent production activity. This redox-potential-dependent behaviour of the hydrogen production activity represents an n = 2-type of redox titration curve with an 'apparent midpoint potential' which corresponds with the potential of the hydrogen electrode at that pH. The effect of pH on the manometrically determined hydrogen production activity (direct) is in good agreement with that determined spectrophotometrically (indirect; see preceding paper), with both electron donors tested. In contrast to predictions from the models for hydrogenase activity [van Dijk et al. (1980) Eur. J. Biochem.102, 317--330], a double-reciprocal plot of the kinetic data for M. elsdenii flavodoxin hydroquinone at pH 5.5 is non-linear. A slightly adapted kinetic model based on a similar mathematical formulation of its rate equation, to explain the effects of redox potential, proton and electron (donor) concentration on the hydrogenase activity is proposed. This model also explains, on a theoretical basis, the effects of pH and redox potential on the hydrogen production activity. The effect of pH on the hydrogen oxidation activity with methyl viologen and benzyl viologen as electron acceptors shows for both dyes an optimum at pH 9.7. The ratio of the activities with both viologens is constant over the ph range tested.
Collapse
|
36
|
The Electron Transport System and Hydrogenase of Paracoccus denitrificans. CURRENT TOPICS IN BIOENERGETICS 1981. [DOI: 10.1016/b978-0-12-152512-5.50009-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
|
37
|
|
38
|
An Evaluation of N2 Fixation and H2 Production in Fermentation Culture. ACTA ACUST UNITED AC 1980. [DOI: 10.1016/b978-0-12-040304-2.50017-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
39
|
Van Dijk C, Mayhew SG, Grande HJ, Veeger C. Purification and properties of hydrogenase from Megasphaera elsdenii. EUROPEAN JOURNAL OF BIOCHEMISTRY 1979; 102:317-30. [PMID: 527582 DOI: 10.1111/j.1432-1033.1979.tb04246.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A hydrogenase has been purified to homogeneity from the soluble fraction of the rumen bacterium Megasphaera elsdenii, the overall purification is 200 times with a yield of 14%. The pure enzyme consists of a single polypeptide chain with Mr approximately 50 000 which contains 12 atoms of non-haem iron and 12 atoms of acid-labile sulphide. The enzyme is rapidly inactivated by O2 and it is therefore purified under nitrogen and in the presence of sodium dithionite. The optical spectrum of the enzyme, after removal of the dithionite with air, shows a peak at 275 nm (epsilon 275 nm = 143 mM-1 cm-1) and a shoulder between 350 nm and 400 nm (epsilon 400 nm = 46 mM-1 cm-1). The enzyme catalyses hydrogen production from sodium dithionite at a low rate. The rate is greatly enhanced by addition of the electron donors flavodoxin, ferredoxin and methyl viologen. The kinetic data with these three electron donors suggest co-operativity, but no indication of self-association of the enzyme was obtained. Sodium chloride enhances the rate of hydrogen production with methyl viologen semiquinone and changes the kinetic behaviour of the enzyme with this electron donor, but causes inhibition of the reactions mediated by ferredoxin and flavodoxin. Two kinetic models were developed which are consistent with the kinetic data of the three electron donors tested. The apparent co-operativity for the hydrogen production can be fitted with the mathematical form of those models. The identical kinetic behaviour of the hydrogenase with the one-electron donors flavodoxin and methyl viologen semiquinone monomer and the two-electron donor ferredoxin indicates that the hydrogenase accepts two electrons in two separate, independent steps and further indicates that the two (4Fe-4S) clusters of the donor ferredoxin are independent. The interpretation of the kinetic data with methyl viologen semiquinone is complicated by the fact that the semiquinone dimerises, and that the formation of the dimer is enhanced by salt. Taking into account the association of this donor, the activity of the enzyme with methyl viologen semiquinone can be described by the sum of the activities of the enzyme with methyl viologen monomer and methyl viologen dimer. The enzyme catalyses the oxidation of hydrogen gas with methyl and benzyl viologen as electron acceptors to their semiquinone forms; both electron acceptors show Michaelis-Menten kinetics. The hydrogen oxidation activity with both electron acceptors is stimulated by addition of sodium chloride. The kinetic data of the oxidation of hydrogen with the two-electron acceptors used are consistent with the porposed models, if it is assumed that the pathway followed is compulsory. At this moment no choice can be made between the models proposed.
Collapse
|
40
|
Arp DJ, Burris RH. Purification and properties of the particulate hydrogenase from the bacteroids of soybean root nodules. BIOCHIMICA ET BIOPHYSICA ACTA 1979; 570:221-30. [PMID: 40601 DOI: 10.1016/0005-2744(79)90142-6] [Citation(s) in RCA: 77] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The uptake hydrogenase (hydrogen:ferricytochrome c3 oxidoreductase, EC 1.12.2.1) from the bacteroids of soybean root nodules infected with Rhizobium japonicum 110 has been purified and characterized. Bacteroids were prepared, then broken by sonication. The particulate enzyme was solubilized by treatment with Triton X-100 and further purified by polyethylene glycol fractionation, DEAE-cellulose and Sephadex G-100 chromatography. The specific activity has been increased 196-fold to 19.6 units/mg protein. The molecular weight is 63 300 as determined by gel filtration and 65 300 as determined by SDS-polyacrylamide gel electrophoresis, indicating that the enzyme is a monomer. The enzyme is O2 sensitive, with a half-life of 70 min when exposed to air. The pH optimum of the solubilized enzyme is near 5.5; the Km for H2 is 1.4 microM. Suitable electron acceptors are methylene blue, ferricyanide, 2,6-dichlorophenolindophenol, and cytochrome c. Benzyl viologen is reduced slowly; methyl viologen, NAD(P)+, FAD, FMN, and O2 are not reduced. The optimum temperature for activity is 65-70 degrees C with an activation energy of 9.2 kcal. H2 evolution by the enzyme has been demonstrated. The hydrogenase is well-suited to function in an environment where all the available H2 is generated in situ.
Collapse
|
41
|
Sim E, Vignais PM. Comparison of the membrane-bound and detergent-solubilised hydrogenase from paracoccus denitrificans. Isolation of the hydrogenase. BIOCHIMICA ET BIOPHYSICA ACTA 1979; 570:43-55. [PMID: 39613 DOI: 10.1016/0005-2744(79)90199-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The hydrogenase from Paracoccus denitrificans is an integral membrane protein and has been solubilised by Triton X-100. The membrane-bound and detergent-solubilised forms of the enzyme have been compared. Both forms of the enzyme show a pH optimum for reduction of benzyl viologen at pH 8.5--9.0 and are both inhibited by concentrations of NaCl greater than 30 mM. An Arrhenius plot of the activity of hydrogenase in the membrane shows no 'break'. The form of the Arrhenius plot and the activation energy are not significantly changed on solubilisation of the enzyme. The Km and V values for benzyl viologen, methyl viologen and H2 are unaltered when the enzyme is extracted from the membrane. Therefore, solubilisation of hydrogenase from the membrane by Triton X-400 is unlikely to disrupt the native conformation of the enzyme. The detergent-solubilised hydrogenase has subsequently been purified using ammonium sulphate precipitation, sucrose density gradient centrifugation and chromatography on hydroxyapatite. The overall yield of activity is 23%, with a final purification of over 100-fold.
Collapse
|
42
|
Klibanov AM, Kaplan NO, Kamen MD. Chelating agents protect hydrogenase against oxygen inactivation. BIOCHIMICA ET BIOPHYSICA ACTA 1979; 547:411-6. [PMID: 111712 DOI: 10.1016/0005-2728(79)90021-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The effect of chelation on rate or air inactivation of hydrogenase from Clostridium pasteurianum has been investigated. All chelating agents used, whether water-soluble or water-insoluble, afforded protection against oxygen inactivation. EDTA appeared to be the most effective. Thus, in the absence of EDTA, hydrogenase in aqueous solution was nearly totally inactivated after 1 hour incubation in air, whereas 0.5 M EDTA (which did not affect significantly catalytic activity) allowed 41% retention of the initial activity even after 3 days incubation.
Collapse
|
43
|
McKellar RC, Sprott GD. Solubilization and properties of a particulate hydrogenase from Methanobacterium strain G2R. J Bacteriol 1979; 139:231-8. [PMID: 37236 PMCID: PMC216850 DOI: 10.1128/jb.139.1.231-238.1979] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mechanical disruption of cells of Methanobacterium strain G2R resulted in a 78-fold increase in the specific activity of the hydrogenase as measured by the benzyl viologen reduction assay. Approximately 50% of the activity in disrupted cells was associated with the particulate fraction. Between 69 and 85% of the particulate hydrogenase was released by treatment with the detergents Triton X-100, deoxycholate, and octyl-beta-d-glucopyranoside. The relative electrophoretic mobilities of the soluble hydrogenases were identical, indicating that G2R possessed a single electrophoretically distinct hydrogenase. The particulate enzyme was inactivated by oxygen and could be reactivated with dithionite or glucose plus glucose oxidase. The enzyme had a pH optimum of 8.5 and resisted heating at 52 but not 77 degrees C. A number of nonspecific dyes, flavin adenine dinucleotide, and riboflavin 5'-phosphate were effective electron acceptors; oxidized nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide phosphate, and factor 420 were apparently not reduced. Hydrogenase activity was inhibited by p-hydroxymercuribenzoate, cyanide, chloroform, and chloramphenicol. The molecular weight of the solubilized enzyme was 900,000, with subunits of molecular weights 38,500, 50,700, and approximately 80,000. It is suggested that, in intact cells of G2R, the large hydrogenase complex is loosely bound to the cell wall or membrane.
Collapse
|