Effects of Carbonic Anhydrase Inhibitors on Proton Exchange and Photosynthesis in Pea Protoplasts |
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Authors: | Ignatova L K Moskvin O V Ivanov B N |
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Institution: | (1) Institute of Basic Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow oblast, 142290, Russia |
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Abstract: | At concentrations of 100–200 M, ethoxyzolamide, a lipophilic inhibitor of carbonic anhydrase, considerably (by 60%) inhibited light-induced CO2-dependent oxygen evolution in pea protoplasts at the optimum concentration of inorganic carbon (100 M CO2) in the medium. At the same concentrations of the inhibitor, electron transport in isolated pea thylakoids was inhibited only by 6–9%. Acetazolamide, a water-soluble inhibitor of carbonic anhydrase, affected neither the rate of CO2-dependent O2evolution in protoplasts nor electron transport in thylakoid membranes. A light-dependent proton uptake by protoplasts was demonstrated. At pH 7.2, the induction kinetics and the rate of proton uptake were similar to those for CO2-dependent O2evolution. The rate of proton uptake was decreased twofold by 1 mM acetazolamide. This fact agrees with the notion that a membrane-bound carbonic anhydrase is operative in the plasma membrane of higher plant cells. A mechanism of its functioning is suggested. Possible functions of carbonic anhydrases in the cells of C3-plants are discussed. |
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Keywords: | Pisum sativum carbonic anhydrase protoplasts thylakoids CO2-dependent O2evolution light-dependent proton fluxes electron transport acetazolamide ethoxyzolamide |
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