Carboxylation reaction catalyzed by 2-oxoglutarate:ferredoxin oxidoreductases from Hydrogenobacter thermophilus |
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Authors: | Masahiro Yamamoto Takeshi Ikeda Hiroyuki Arai Masaharu Ishii Yasuo Igarashi |
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Institution: | (1) Department of Biotechnology, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan |
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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 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. |
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Keywords: | |
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