Tetrahydromethanopterin, a coenzyme involved in autotrophic acetyl coenzyme A synthesis from 2 CO<sub>2</sub> in <i>Methanobacterium</i>

Länge, Siegfried; Fuchs, Georg

doi:10.1016/0014-5793(85)80281-7

Cited by 23 publications

(9 citation statements)

References 19 publications

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“…2) and that of acetyl-CoA synthesis (bottom of Fig. 2); (iii) that H 2 is the electron donor since growth is on CO 2 and H2; (iv) that methyltetrahydromethanopterin (H4MPT) is the methyl donor to [Co]E. This latter suggestion is in accord with the recent demonstration by Lange and Fuchs [57] showing that methenyl-H4MPT is converted to the methyl of acetyl-CoA by an extract of M.…”

Section: H#)supporting

confidence: 84%

The acetyl-CoA pathway of autotrophic growth

Wood

Ragsdale

Pezacka

1986

FEMS Microbiology Letters

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The most direct conceivable route for synthesis of multicarbon compounds from CO: is to join two molecules of CO 2 together to make a 2-carbon compound and then polymerize the 2-carbon compound or add CO 2 successively to the 2-carbon compound to make multicarbon compounds. Recently, it has been demonstrated that the bacterium, Clostridium thermoaceticum, grows autotrophically by such a process. The mechanism involves the reduction of one molecule of CO 2 to a methyl group and then its combination with a second molecule of CO2 and CoA to form acetyl-CoA. We have designated this autotrophic pathway the acetyl-CoA pathway [1]. Evidence is accumulating that this pathway is utilized by other bacteria that grow with CO 2 and H 2 as the source of carbon and energy. This group includes bacteria which, like C. thermoaceticum, produce acetate as a major end product and are called acetogens or acetogenic bacteria. It also includes the methaneproducing bacteria and sulfate-reducing bacteria.The purpose of this review is to examine critically the evidence that the acetyl-CoA pathway occurs in other bacteria by a mechanism that is the same or similar to that found in C. thermoaceticum. For this purpose, the mechanism of the acetyl-CoA pathway, as found in C. thermoaceticum, is described and hypothetical mecha-nims for other organisms are presented based on the acetyl-CoA pathway of C. thermoaceticum. The available data have been reviewed to determine if the hypothetical schemes are in accord with presently known facts. We conclude that the formation of acetyl-CoA by other acetogens, the methanogens and sulphate-reducing bacteria occurs by a mechanism very similar to that of C.therrnoaceticum.

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Section: H#)supporting

confidence: 84%

The acetyl-CoA pathway of autotrophic growth

Wood

Ragsdale

Pezacka

1986

FEMS Microbiology Letters

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“…In extracts of Methanobacterium thermoautotrophicum, methyl-CoM stimulates acetyl-CoA synthesis from C02, presumably because it stimulates CO2 reduction to methyl-THMPT and CH4 (19,30,37,44). Likewise, the inhibitor of the methyl-CoM reductase system, BES, inhibits acetylCoA synthesis because it prevents reduction of CO2 (44).…”

Section: Resultsmentioning

confidence: 99%

“…In other methanogens, THMPT and CO are C-1 donors for autotrophic acetyl-CoA biosynthesis (30,31). CH20 condenses with THMPT to form methylene-THMPT in extracts, and it is an intermediate in methanogenesis or incorporated into the methyl group of acetyl-CoA (12,31).…”

Section: Resultsmentioning

confidence: 99%

“…Labeling studies have shown that the biosynthesis of acetyl-CoA in Methanobacterium thermoautotrophicum resembles the total synthesis of acetyl-CoA from 2CO2 by acetogens. The methyl group of acetate comes from methyltetrahydromethanopterin (methyl-THMPT), which is a folate analog and an intermediate in the reduction of CO2 to methane (11,28,30,45). The carboxy group of acetyl-CoA is derived from another molecule of C02, which is reduced to a bound CO by CO dehydrogenase, or it can come directly from carbon * Corresponding author.…”

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confidence: 99%

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Autotrophic acetyl coenzyme A biosynthesis in Methanococcus maripaludis

Shieh

Whitman

1988

J Bacteriol

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To detect autotrophic CO2 assimilation in cell extracts of Methanococcus maripaludis, lactate dehydrogenase and NADH were added to convert pyruvate formed from autotrophically synthesized acetyl coenzyme A to lactate. The lactate produced was determined spectrophotometrically. When CO2 fixation was pulled in the direction of lactate synthesis, CO2 reduction to methane was inhibited. Bromoethanesulfonate (BES), a potent inhibitor of methanogenesis, enhanced lactate synthesis, and methyl coenzyme M inhibited it in the absence of BES. Lactate synthesis was dependent on CO2 and 112, but H2 + C02-independent synthesis was also observed.In cell extracts, the rate of lactate synthesis was about 1.2 nmol min-' mg of protein-'. When BES was added, the rate of lactate synthesis increased to 2.3 nmol min-' mg of protein-'. Because acetyl coenzyme A did not stimulate lactate synthesis, pyruvate synthase may have been the limiting activity in these assays. Radiolabel from '4CO2 was incorporated into lactate. The percentages of radiolabel in the C-1, C-2, and C-3 positions of lactate were 73, 33, and 11%, respectively. Both carbon monoxide and formaldehyde stimulated lactate synthesis. 14CH20 was specifically incorporated into the C-3 of lactate, and 14CO was incorporated into the C-1 and C-2 positions. Low concentrations of cyanide also inhibited autotrophic growth, CO dehydrogenase activity, and autotrophic lactate synthesis. These observations are in agreement with the acetogenic pathway of autotrophic CO2 assimilation.Most species of methanogenic bacteria can oxidize hydrogen and reduce carbon dioxide to methane to obtain energy for growth (26,47). In addition, about one-half of the species of methanogens which have been described are able to grow autotrophically. Nevertheless, the pathway of CO2 fixation during autotrophic growth in methanogens has not been fully established, and the carbon metabolism of only a few species has been characterized. In Methanobacterium thermoautotrophicum and Methanosarcina barkeri, a novel pathway of acetyl coenzyme A (acetyl-CoA) synthesis from two molecules of CO2 has been proposed (16,21,29,(42)(43)(44). This pathway closely resembles the total synthesis of acetate described previously in Clostridium thermoaceticum and other anaerobic eubacteria (8,13,22,24,25,32,33,50).The acetyl-CoA pathway in C. thermoaceticum involves total synthesis of acetate from two molecules of CO2 via different routes of reduction (32, 50). One molecule of CO2 is reduced to the methyl level via the folate pathway, and the other molecule of CO2 is reduced to a bound CO residue. They are then condensed to an activated acetyl residue which is thiolized with HS-CoA. The final step of acetylCoA biosynthesis is catalyzed by CO dehydrogenase (36).In Methanobacterium thermoautotrophicum, acetyl-CoA is an early product of CO2 assimilation (15,17,38). Labeling studies have shown that the biosynthesis of acetyl-CoA in Methanobacterium thermoautotrophicum resembles the total synthesis of acetyl-CoA from 2CO2 by acetogens....

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“…Factor 111 was isolated from whole cells, cell extract, I00000 x g supernatant of cell extract, and the 45 -60% (NH4)2S04 protein fraction of the I00000 x g supernatant of cell extract. Tetrahydromethanopterin was isolated under anoxic, acidic conditions from boiled cell extract of 200 g fresh cells essentially as described [24,28]. All steps except HPLC were performed anaerobically in an anaerobic chamber with 95% Nz, 5% Hz gas phase.…”

Section: Preparation Of Cell Extract and Protein Fractionationmentioning

confidence: 99%

Autotrophic synthesis of activated acetic acid from CO₂ in Methanobacterium thermoautotrophicum

Länge¹,

Fuchs²

1987

European Journal of Biochemistry

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The synthesis of acetyl-CoA from C02, H2, and various C1 compounds was studied in vitro with extracts and with protein fractions of Methanobacterium thermoautotrophicum. Acetyl-CoA synthesis from C 0 2 and H2 by extracts required C 0 2 reduction to CH4 to proceed. Both processes were highly stimulated by formaldehyde which served as the carbon precursor of both CH4 and the CH3 group of acetate. Carbon monoxide in combination with formaldehyde dramatically stimulated the acetyl-CoA synthesis up to 1 %-fold. In t h s system, which did not require C 0 2 reduction to the formaldehyde and CO level, acetyl-CoA synthesis was no longer dependent on CH4 formation. The soluble (100000 x g supernatant) cell protein was resolved into a protein fraction [45-60% (NH4),S04-fraction] which catalyzed acetyl-CoA synthesis at a specific rate of 15 nmol . min-' . (equivalent of mg cell protein)-' (60 "C). This oxygen-sensitive enzyme reaction required dithioerythritol for activity and was strictly dependent on (a) coenzyme A, (b) CO, and (c) N5,N"-methylene tetrahydromethanopterin, N5-methyl tetrahydromethanopterin or formaldehyde plus tetrahydromethanopterin. The incorporation of formaldehyde is explained by the spontaneous formation of methylene tetrahydromethanopterin. The product of the reaction, acetyl-CoA, was quantitatively derived from CO (carboxyl of acetate) and a C1 derivative of tetrahydromethanopterin (methyl of acetate). The C1 derivative of tetrahydromethanopterin could not be replaced by a C1 derivative of tetrahydrofolate or by methyl-coenzyme M; ATP was not required. The active protein fraction contained CO dehydrogenase and at least one corrinoid protein. These results provide strong biochemical arguments for the proposed mechanism of autotrophic acetyl-CoA synthesis in Methanobacterium.Methanogenic bacteria are strict anaerobic archaebacteria which in general are able to obtain energy simply from the reduction of C 0 2 with H2 (C02 + 4 H2 --t CH4 + 2 H20).Most species grow autotrophically, i.e. in addition they use CO, as sole carbon compound for biosyntheses [I]. In Methanobacterium thermoautotrophicum, a thermophilic microorganism [2], C 0 2 assimilation does not proceed via the pentose phosphate cycle (Calvin cycle) [3 -81. Rather, a novel non-cyclic pathway for a de novo synthesis of acetyl-coenzyme A from 2 C 0 2 + 4 H2 was established termed the 'acetylCoA pathway' [8 -1 I]. This process was found to have many features in common with acetate synthesis from CO, in the acetogenic bacterium Clostridium thermoaceticum (for reviews see [12-141. C. thermoaceticum ferments hexoses to acetates: two acetate molecules are generated from two pyruvate molecules and one from (20,. The validity of this model was questioned when carbon monoxide was found to replace pyruvate as C 0 2 donor, and acetylCoA was shown to be the reaction product [16]. Studies by the laboratory of Thauer [17 -201 had indicated that the nickel enzyme carbon monoxide dehydrogenase is involved in this process. It is now postulated that CO dehy...

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Tetrahydromethanopterin, a coenzyme involved in autotrophic acetyl coenzyme A synthesis from 2 CO₂ in Methanobacterium

Cited by 23 publications

References 19 publications

The acetyl-CoA pathway of autotrophic growth

The acetyl-CoA pathway of autotrophic growth

Autotrophic acetyl coenzyme A biosynthesis in Methanococcus maripaludis

Autotrophic synthesis of activated acetic acid from CO₂ in Methanobacterium thermoautotrophicum

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Tetrahydromethanopterin, a coenzyme involved in autotrophic acetyl coenzyme A synthesis from 2 CO2 in Methanobacterium

Cited by 23 publications

References 19 publications

The acetyl-CoA pathway of autotrophic growth

The acetyl-CoA pathway of autotrophic growth

Autotrophic acetyl coenzyme A biosynthesis in Methanococcus maripaludis

Autotrophic synthesis of activated acetic acid from CO2 in Methanobacterium thermoautotrophicum

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Tetrahydromethanopterin, a coenzyme involved in autotrophic acetyl coenzyme A synthesis from 2 CO₂ in Methanobacterium

Autotrophic synthesis of activated acetic acid from CO₂ in Methanobacterium thermoautotrophicum