Autotrophic acetyl coenzyme A biosynthesis in Methanococcus maripaludis
To detect autotrophic CO/sub 2/ assimilation in cell extracts of Methanococcus maripaludis, lactate dehydrogenase and NADH were added to convert pyruvate formed from autotropically synthesized acetyl coenzyme A to lactate. The lactate produced was determined spectrophotometrically. When CO/sub 2/ fixation was pulled in the direction of lactate synthesis, CO/sub 2/ reduction to methane was inhibited. Bromoethanesulfonate (BES), a potent inhibitor of methanogenesis, enhanced lactate synthesis, and methyl coenzyme M inhibited it in the absence of BES. Lactate synthesis was dependent on CO/sub 2/ and H/sub 2/, but H/sub 2/ + CO/sub 2/-independent synthesis was also observed. In cell extracts, the rate of lactate synthesis was about 1.2 nmol min/sup -1/ mg of protein/sup -1/. When BES was added, the rate of lactate synthesis increased to 2.1 nmol min/sup -1/ mg of protein/sup -1/. Because acetyl coenzyme A did not stimulate lactate synthesis, pyruvate synthase may have been the limiting activity in these assays. Radiolabel from /sup 14/CO/sub 2/ was incorporated into lactate. The percentages of radiolabel in the C-1, C-2, and C-3 positions of lactate were 73, 33, and 11%, respectively. Both carbon monoxide and formaldehyde stimulated lactate synthesis. /sup 14/CH/sub 2/O was specifically incorporated into the C-3 of lactate, and /sup 14/CO was incorporated into the C-1 and C-2 positions. Low concentrations of cyanide also inhibited autotrophic growth, CO dehydrogenase activity, and autotrophic lactate synthesis. These observations are in agreement with the acetogenic pathway of autotrophic CO/sub 2/ assimilation.
- Research Organization:
- Univ. of Georgia, Athens (USA)
- OSTI ID:
- 6583324
- Journal Information:
- J. Bacteriol.; (United States), Vol. 170:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARBON DIOXIDE FIXATION
BIOLOGICAL PATHWAYS
COENZYMES
BIOSYNTHESIS
LACTATES
METHANOGENIC BACTERIA
GROWTH
CARBON 14 COMPOUNDS
INHIBITION
LACTATE DEHYDROGENASE
RESPONSE MODIFYING FACTORS
TRACER TECHNIQUES
BACTERIA
CARBOXYLIC ACID SALTS
ENZYMES
HEMIACETAL DEHYDROGENASES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MICROORGANISMS
OXIDOREDUCTASES
SYNTHESIS
550201* - Biochemistry- Tracer Techniques