The inhibition of the carbon concentrating mechanism of the green alga Chlorella saccharophila by acetazolamide |
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Authors: | Pollock Steve Vincent Colman Brian |
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Affiliation: | Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA;Department of Biology, York University, 4700 Keele St., Toronto, Ontario, M3J 1P3, Canada |
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Abstract: | The effects of the carbonic anhydrase (CA) inhibitors acetazolamide (AZ) and dextran-bound sulfonamide (DBS) on HCO3−-dependent O2 evolution in Chlorella saccharophila were evaluated. Addition of 4 μ M AZ or 0.4 mg ml−1 DBS to photosynthesizing cells reduced the O2 evolution rate at low dissolved inorganic carbon (DIC) concentration, decreased the size of the intracellular acid-labile carbon pool, and decreased the apparent affinity of the cells for DIC. Measurement of the whole-cell affinity of cells for CO2 and HCO3− in the presence and absence of inhibitors indicated that active HCO3− transport was inhibited by AZ and DBS. The inhibition of HCO3− transport was independent of the inhibition of external and internal CA. These results suggest that the active uptake of HCO3− occurs initially by the interaction of HCO3− and a CA-like transporter. |
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