Ribulose-1,5-bisphosphate carboxylase/oxygenase from thermophilic red algae with a strong specificity for CO2 fixation
Uemura, K.; Anwaruzzaman; Miyachi, S.; Yokota, A.
Biochemical and Biophysical Research Communications 233(2): 568-571
1997
ISSN/ISBN: 0006-291X PMID: 9144578 Document Number: 477803
Strongly carboxylase-specific ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) was found in Galdieria partita and Cyanidium caldarium (Cyanidiophyceae). The relative specificity, V-cK-o/V-oK-c, of Galdieria and Cyanidium RuBisCO was 238 and 222, respectively; 2.4 to 2.5-fold that of higher plant RuBisCOs. The apparent K-m of RuBisCO from the thermophilic red algae for CO-2 was 6 to 7 mu-M 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 cntdot 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.