Electron-transport chain and coupled oxidative phosphorylation in methanol-grown Paracoccus denitrificans |
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Authors: | H W Van Verseveld A H Stouthamer |
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Institution: | (1) Department of Microbiology, Biological Laboratory, Free University, De Boelelaan 1087, Amsterdam, The Netherlands |
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Abstract: | Methanol dehydrogenase of Paracoccus denitrificans was shown to be very similar to the enzyme of Pseudomonas sp, M. 27. The K
m value for methanol with excess activator (ammonium ions) is 35 M. The pH optimum for enzyme activity with 2,6-dichlorophe-nolindophenol as electronacceptor was at 9.0 A CO-binding type of cytochrome c was present only in cells grown with methanol as carbon and energy source.It has been shown that methanol-oxidation involves electron-transport via cytochrome c and an a-type cytochrome to oxygen. Antimycin A did not inhibit this electron transport and 90% inhibition was obtained by 375 M potassium cyanide. Electron transport from endogenous substrates is possible via cytochrome b and possibly cytochrome o to oxygen. Potassium cyanide inhibited 90% of the electron transport via this pathway at a concentration of 1.42 mM. Measurement of respiration-driven proton translocation proved that during oxidation of methanol to formaldehyde by oxygen one mole of adenosine triphosphate is synthesized in the site 3 region of the electron transport chain. The H+/O value found confirmed the H+/site ratio of 3–4 found in heterotrophic grown cells. During electron transport from endogenous substrates to oxygen there is a possible synthesis of 3 moles of adenosine triphosphate.In heterotrophically grown cells electron transfer to oxygen follows almost only the branch of the respiratory chain containing cytochrome o. In methanol-grown cells the pathway via the a-type cytochrome seems more important.Abbreviations DCPIP
2,6-dichlorophenolindophenol
- PMS
phenazine methosulphate
- EPR
electron paramagnetic resonance
- S.D.
standard deviation
- ATP
adenosine triphosphate |
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Keywords: | Methanol dehydrogenase Autotrophic growth Electron transport chain Oxidative phosphorylation Proton translocation Paracoccus denitrificans |
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