Carbonic anhydrase located on cell surface increases the affinity for inorganic carbon in photosynthesis of <i>Dunaliella tertiolecta</i>

Abstract

Low‐CO 2 cells of Dunaliella tertiolecta had higher carbonic anhydrase (CA) activity on their surfaces than inside. The treatment with subtilisin completely abolished CA activity on the cell surface, while the activity inside the cells was not affected by this treatment. Correspondingly, the apparent K m (NaHCO 3 ) for photosynthesis was increased two‐fold, while V max was not affected by this treatment. The apparent K m (NaHCO 3 ) was lowered to the original level when CA was added to the suspension of subtilisin‐treated cells. These results indicate that CA on the cell surface enhances the affinity for inorganic carbon in photosynthesis of D. tertiolecta .