Inorganic Carbon Transport and Fixation in Cells of Anabaena variabilis Adapted to Mixotrophic Conditions

概要

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The cyanobacterium Anabaena variabilis ATCC 29413 grown at low CO_2 concentration under mixotrophic conditions with fructose showed a repression in the ability to fix inorganic carbon. This repression was not due to a diminution in the ability to transport external inorganic carbon but could be explained by a decrease of two enzymatic activities involved in the assimilation of inorganic carbon: carbonic anhydrase and Rubisco. Carbonic anhydrase activity was close to 50% lower in mixotrophic than in autotrophic cells. Moreover growth under mixotrophic conditions reduced Rubisco activity at all dissolved inorganic carbon concentrations assayed (5-60 mM). Maximun Rubisco activity (V_lt;max>) decreased from 4.7 μmol CO_2 mg protein ^<-1>h^<-1> in autotrophic cells to 2.3 μmol CO_2 mg protein ^<-1>h^<-1> in mixotrophic cells. No significant differences in K_m (C_i) between autotrophic and mixotrophic cells were however observed. The possible mechanisms involved in the inhibition of Rubisco are discussed.
日本植物生理学会の論文