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

Extremophiles. 2010 Jan;14(1):79-85. doi: 10.1007/s00792-009-0289-4. Epub 2009 Nov 6.

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 K (m) 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.

MeSH terms

  • Acyl Coenzyme A / chemistry*
  • Acyl Coenzyme A / metabolism
  • Bacteria / enzymology*
  • Bacteria / genetics
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Citric Acid Cycle / physiology
  • Genome, Bacterial / physiology
  • Ketone Oxidoreductases / chemistry*
  • Ketone Oxidoreductases / genetics
  • Ketone Oxidoreductases / metabolism
  • Kinetics

Substances

  • Acyl Coenzyme A
  • Bacterial Proteins
  • succinyl-coenzyme A
  • Ketone Oxidoreductases
  • 2-oxoglutarate synthase