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Autotrophic acetyl coenzyme A biosynthesis in Methanococcus maripaludis
1Department of Microbiology, University of Georgia, Athens 30602.
Journal of Bacteriology
|July 1, 1988
Summary
Methanococcus maripaludis uses an acetogenic pathway for carbon dioxide assimilation, converting CO2 and H2 into lactate. This process was confirmed by tracking radiolabeled carbon and observing inhibition by cyanide.
Area of Science:
- Microbiology
- Biochemistry
- Metabolic Pathways
Background:
- Methanococcus maripaludis is an archaeon known for methanogenesis.
- Understanding its autotrophic CO2 assimilation is crucial for microbial metabolism research.
Purpose of the Study:
- To investigate the autotrophic CO2 assimilation pathway in Methanococcus maripaludis cell extracts.
- To identify key enzymes and intermediates involved in carbon fixation.
Main Methods:
- Enzymatic conversion of acetyl-CoA to lactate using lactate dehydrogenase and NADH.
- Spectrophotometric determination of lactate production.
- Inhibition studies using bromoethanesulfonate (BES) and methyl coenzyme M.
- Radiolabeling experiments with 14CO2, 14CH2O, and 14CO.
- Enzyme activity assays and growth inhibition studies with cyanide.
Main Results:
- Lactate synthesis was observed, indicating CO2 assimilation.
- Bromoethanesulfonate (BES) enhanced lactate synthesis, while methyl coenzyme M inhibited it.
- Radiolabel from 14CO2 was incorporated into lactate, with specific labeling patterns at C-1, C-2, and C-3.
- Carbon monoxide and formaldehyde also stimulated lactate synthesis, with distinct incorporation sites.
- Cyanide inhibited autotrophic growth, CO dehydrogenase activity, and lactate synthesis.
Conclusions:
- The results support an acetogenic pathway for autotrophic CO2 assimilation in Methanococcus maripaludis.
- Pyruvate synthase may be a rate-limiting enzyme in this pathway.
- The study provides insights into the carbon flow and metabolic flexibility of this archaeon.