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Biochem Biophys Res Commun. 1997 Apr 17;233(2):568-71.

Ribulose-1,5-bisphosphate carboxylase/oxygenase from thermophilic red algae with a strong specificity for CO2 fixation.

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  • 1Plant Molecular Physiology Laboratory, Research Institute of Innovative Technology for the Earth (RITE), Kizu, Kyoto, Japan.


Strongly carboxylase-specific ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) was found in Galdieria partita and Cyanidium caldarium (Cyanidiophyceae). The relative specificity, VcKo/VoKc, of Galdieria and Cyanidium RuBisCO was 238 and 222, respectively; 2.4 to 2.5-fold that of higher plant RuBisCOs. The apparent Km of RuBisCO from the thermophilic red algae for CO2 was 6 to 7 microM and the smallest of the values reported so far for other RuBisCOs. The pre-rhodophyte Porphiridium purpureum, which lives at moderate temperatures, had RuBisCO with the relative specificity value of 144. A large difference (5.2 kcal x mol(-1)) in the activation energies between the carboxylase and oxygenase activities in Galdieria RuBisCO was a cause of the strong specificity for the carboxylase activity.

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