Original Paper

Extremophiles

, Volume 14, Issue 1, pp 79-85

First online:

Carboxylation reaction catalyzed by 2-oxoglutarate:ferredoxin oxidoreductases from Hydrogenobacter thermophilus

  • Masahiro YamamotoAffiliated withDepartment of Biotechnology, University of Tokyo
  • , Takeshi IkedaAffiliated withDepartment of Biotechnology, University of Tokyo
  • , Hiroyuki AraiAffiliated withDepartment of Biotechnology, University of Tokyo
  • , Masaharu IshiiAffiliated withDepartment of Biotechnology, University of Tokyo Email author 
  • , Yasuo IgarashiAffiliated withDepartment of Biotechnology, University of Tokyo

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Abstract

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.

Keywords

Hydrogenobacter thermophilus 2-Oxoglutarate:ferredoxin oxidoreductase Reductive tricarboxylic acid cycle Carboxylation Pyruvate:ferredoxin oxidoreductase