Abstract
Cell suspensions of Methanosarcina barkeri, grown on acetate, catalyzed the conversion of carbon monoxide and H2O to CO2 and H2 in stoichiometric amounts when methane formation was inhibited by bromoethanesulfonate. The specific activity was 80-120 nmol min-1 mg protein-1 at 5% CO in the gas phase. CO oxidation was coupled with the phosphorylation of ADP as indicated by a rapid increase of the intracellular ATP level upon start of the reaction. At least 0.1 mol ATP was formed/mol CO consumed. The onset of CO oxidation was also accompanied by an increase of the proton motive force (delta p) from 100 mV to 150 mV (inside negative). Addition of the uncoupler tetrachlorosalicylanilide to CO-metabolizing cells led to a rapid decrease of the ATP level and of delta p, and to an increase of the CO oxidation rate up to 70%. In the presence of the proton-translocating ATPase inhibitor N,N'-dicyclohexylcarbodiimide the phosphorylation of ADP was inhibited and CO oxidation slowed down, whereas delta p was almost unaffected. Inhibition of CO oxidation under these conditions was relieved by the addition of the protonophore tetrachlorosalicylanilide. The results indicate that in acetate-grown M. barkeri the free-energy change associated with the formation of CO2 and H2 from CO and H2O (delta G degrees = -20 kJ/mol) can be used to drive the phosphorylation of ADP and that the coupling proceeds via a chemiosmotic mechanism. A possible role of the carbon monoxide oxidation reaction as an energy-conserving site in acetate fermentation to CH4 and CO2 is discussed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.