Short-Term Regulation of the Nitrogenase Activity in Rhodopseudomonas sphaeroides
| Autor: | Klaas J. Hellingwerf, Cees Veeger, Huub Haaker, Colja Laane, Wil N. Konings, Berend Houwer |
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| Rok vydání: | 2005 |
| Předmět: |
Membrane potential
Cytoplasm biology Nitrogenase Rhodobacter sphaeroides biology.organism_classification Biochemistry Electron transport chain Ammonium Chloride Membrane Potentials Adenosine Diphosphate Electron Transport Light intensity chemistry.chemical_compound Adenosine Triphosphate chemistry Glutamine synthetase Electrochemistry Adenosine triphosphate Intracellular |
| Zdroj: | European Journal of Biochemistry. 127:639-646 |
| ISSN: | 1432-1033 0014-2956 |
| Popis: | The nitrogenase activity in whole cells of Rhodopseudomonas sphaeroides could be inhibited by lowering the electrical potential across the cytoplasmic membrane. The membrane potential was partly dissipated either by lowering the light intensity or by the addition of a lipophilic cation, tetraphenylphosphonium. Under these circumstances, it was shown that the intracellular ATP/ADP ratio was not affected and that the inhibition of the whole cell nitrogenase activity was not due to an inactivation of the nitrogenase enzyme. From these results it is concluded that electron transport to nitrogenase in Rps. sphaeroides is dependent on a high membrane potential. The nitrogenase enzyme in whole cells could be inactivated by lowering the membrane potential across the cytoplasmic membrane by incubating the cells in the dark or in the light in the presence of uncouplers. Nitrogenase could be reactivated in the light in the absence of uncouplers. Some possible mechanisms of action of NH+4 inhibition of whole cell nitrogenase activity could be excluded. Inhibition by NH4Cl of whole cell nitrogenase activity in Rps. sphaeroides could neither be explained by a rapid inactivation of the nitrogenase enzyme, nor by an effect on the intracellular ATP/ADP ratio or the membrane potential. NH+4 inhibits whole cell nitrogenase activity not directly but probably after being assimilated by glutamine synthetase. The role of glutamine, glutamate and 2-oxoglutarate on the regulation of electron transport to nitrogenase will be discussed. |
| Databáze: | OpenAIRE |
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