Carboxylation reaction catalyzed by 2-oxoglutarate:ferredoxin oxidoreductases from Hydrogenobacter thermophilus
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- Yamamoto, M., Ikeda, T., Arai, H. et al. Extremophiles (2010) 14: 79. doi:10.1007/s00792-009-0289-4
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Hydrogenobacter thermophilus TK-6 is a thermophilic, chemolithoautotrophic, hydrogen-oxidizing bacterium that fixes carbon dioxide via the reductive tricarboxylic acid (rTCA) cycle. 2-Oxoglutarate:ferredoxin oxidoreductase (OGOR) is the key enzyme in this cycle that fixes carbon dioxide. The genome of strain TK-6 encodes at least two distinct OGOR enzymes, termed For and Kor. We report here a method for measuring the carboxylation of succinyl-CoA catalyzed by OGORs. The method involves the in vitro coupling of OGOR with ferredoxin and pyruvate:ferredoxin oxidoreductase from strain TK-6, and glutamate dehydrogenase from Sulfolobus tokodaii. Using this method, we determined both the apparent maximum velocities and the Km values of For and Kor for the carboxylation of succinyl-CoA. This is the first reported kinetic analysis of carbon fixation catalyzed by OGOR enzymes from the rTCA cycle.
KeywordsHydrogenobacter thermophilus 2-Oxoglutarate:ferredoxin oxidoreductase Reductive tricarboxylic acid cycle Carboxylation Pyruvate:ferredoxin oxidoreductase
Reductive tricarboxylic acid