Struktur und Funktion des energieumwandelnden Systems der Mitochondrien

Jagow, Gebhard von; Engel, Wolf Dieter

doi:10.1002/ange.19800920906

Cited by 24 publications

(4 citation statements)

References 183 publications

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“…The essential postulate of the Mitchell hypothesis of respiratory ATP synthesis is that ATP formation is coupled to a vectorial transport of charged groups, typically protons, across a semipermeable membrane (79). Today, it has been widely accepted that three protons cross the membrane per molecule of ATP hydrolyzed, no matter whether bacterial (71) or mitochondrial (41,127) membranes are studied. As a consequence, the equivalent of one ATP unit is no longer regarded as the smallest quantum of energy a living cell can make use of.…”

Section: Energetics Of Atp Formationmentioning

confidence: 99%

Energetics of syntrophic cooperation in methanogenic degradation

Schink

1997

Microbiol Mol Biol Rev

479

190

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Fatty acids and alcohols are key intermediates in the methanogenic degradation of organic matter, e.g., in anaerobic sewage sludge digestors or freshwater lake sediments. They are produced by classical fermenting bacteria for disposal of electrons derived in simultaneous substrate oxidations. Methanogenic bacteria can degrade primarily only one-carbon compounds. Therefore, acetate, propionate, ethanol, and their higher homologs have to be fermented further to one-carbon compounds. These fermentations are called secondary or syntrophic fermentations. They are endergonic processes under standard conditions and depend on intimate coupling with methanogenesis. The energetic situation of the prokaryotes cooperating in these processes is problematic: the free energy available in the reactions for total conversion of substrate to methane attributes to each partner amounts of energy in the range of the minimum biochemically convertible energy, i.e., 20 to 25 kJ per mol per reaction. This amount corresponds to one-third of an ATP unit and is equivalent to the energy required for a monovalent ion to cross the charged cytoplasmic membrane. Recent studies have revealed that syntrophically fermenting bacteria synthesize ATP by substrate-level phosphorylation and reinvest part of the ATP-bound energy into reversed electron transport processes, to release the electrons at a redox level accessible by the partner bacteria and to balance their energy budget. These findings allow us to understand the energy economy of these bacteria on the basis of concepts derived from the bioenergetics of other microorganisms.

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Section: Energetics Of Atp Formationmentioning

confidence: 99%

Energetics of syntrophic cooperation in methanogenic degradation

Schink

1997

Microbiol Mol Biol Rev

479

190

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“…The essential postulate of the Mitchell hypothesis of respirative ATP synthesis is that ATP formation is coupled to a vectorial transport of charged groups, typically protons, across a semipermeable membrane. Today it has been widely accepted that three protons cross the membrane per ATP formed or hydrolyzed, no matter whether bacterial [6] or mitochondrial [7,8] membranes are studied. This bears the consequence that no longer the equivalent of one ATP unit has to be regarded as the smallest quantum of energy a living cell can make use of, but that an energy quantum as small as one-third of an ATP equivalent can still be converted into ATP and, as a result, to metabolically useful energy.…”

Section: Energetics Of Atp Formationmentioning

confidence: 99%

Energetics of syntrophic fatty acid oxidation

Schink

1994

FEMS Microbiology Reviews

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Fatty acids are key intermediates in methanogenic degradation of organic matter in sediments as well as in anaerobic reactors. Conversion of butyrate or propionate to acetate, (CO2), and hydrogen is endergonic under standard conditions, and becomes possible only at low hydrogen concentrations (10 4--10-5 bar). A model of energy sharing between fermenting and methanogenic bacteria attributes a maximum amount of about 20 kJ per mol reaction to each partner in this syntrophic cooperation system. This amount corresponds to synthesis of only a fraction (one-third) of an ATP to be synthesized per reaction. Recent studies on the biochemistry of syntrophic fatty acid-oxidizing bacteria have revealed that hydrogen release from butyrate by these bacteria is inhibited by a protonophore or the ATPase inhibitor DCCD (N,N'-dicyclohexyl carbodiimide), indicating that a reversed electron transport step is involved in butyrate or propionate oxidation. Hydrogenase, butyryl-CoA dehydrogenase, and succinate dehydrogenase acitivities were found to be partially associated with the cytoplasmic membrane fraction. Also glycolic acid is degraded to methane and CO 2 by a defined syntrophic coculture. Here the most difficult step for hydrogen release is the glycolate dehydrogenase reaction (E~=-92 mV). Glycolate dehydrogenase, hydrogenase, and ATPase were found to be membrane-bound enzymes. Membrane vesicles produced hydrogen from glycolate only in the presence of ATP; protonophores and DCCD inhibited this hydrogen release. This system provides a suitable model to study reversed electron transport in interspecies hydrogen transfer between fermenting and methanogenic bacteria in methanogenic biomass degradation.

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“…Intrinsically, porphyrins are biogenic molecules responsible for various biological processes such as photosynthesis and respiration [19][20][21][22][23][24][25][26][27][28][29]. Porphyrins have wide applications in solar energy harvesting and artificial photosynthesis [7][8][9][12][13][14][15][16][30][31][32], industrial processes as catalysts [1][2][3][4]6,[33][34][35], photodynamic therapy [11,17,36], anticancer pharmaceutical drugs [10] and photodynamic destruction of viruses [5,37].…”

Section: Introductionmentioning

confidence: 99%