Role of carbonic anhydrase in photosynthetic CO_2 fixation in Chlorella
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概要
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Chlorella vulgaris llh cells grown in air enriched with 4% CO_2 (high-CO_2 cells) had carbonic anhydrase (CA) activity which was 20 to 90 times lower than that of algal cells grown in ordinary air (containing 0.04% CO_2, low-CO_2 cells). The CO_2 concentration during growth did not affect either ribulose 1,5-bisphosphate (RuBP) carboxylase activity or its Km for CO_2. When high-CO_2 cells were transferred to low CO_2 conditions, CA activity increased without a lag period, and this increase was accompanied by an increase in the rate of photosynthetic ^<14>CO_2 fixation under ^<14>CO_2-limiting conditions. On the other hand, CA activity as well as the rate of photosynthetic ^<14>CO_2 fixation at low ^<14>CO_2 concentrations decreased when low-CO_2 cells were transferred to high CO_2 conditions. Diamox, an inhibitor of CA, at 0.1 m_M did not affect photosynthesis of low-CO_2 cells at high CO_2 concentration (0.5%). Diamox inhibited photosynthesis only under low CO_2 concentrations, and the lower the CO_2 concentration, the greater was the inhibition. Consequently, the CO_2 concentration at which the rate of photosynthesis attained one-half its maximum rate (Km) greatly increased in the presence of this inhibitor. When CO_2 concentration was higher than 1%, the photosynthetic rate in low-CO_2 cells decreased, while that in high-CO_2 cells increased. Fractionation of the low-CO_2 cells in non-aqueous medium by density showed that CA was fractionated in a manner similar to the distribution of chlorophyll and RuBP carboxylase. These observations indicate that CA enhances photosynthesis under CO_2-limiting conditions, but inhibits it at CO_2 concentrations higher than a certain level. The mechanism underlying the above regulatory functions of CA is discussed.
- 日本植物生理学会の論文
著者
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Hogetsu Daisuke
Radioisotope Centre Of Applied Microbiology. University Of Tokyo:tokyo Metropolitan Isotope Research
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Miyachi Shigetoh
Radioisotope Centre University Of Tokyo:institute Of Applied Microbiology. University Of Tokyo
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Miyachi Shigetoh
Radioisotope Centre And Institute Of Applied Microbiology University Of Tokyo
関連論文
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- Ammonia Induces Starch Degradation in Chlorella Cells
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- Form of inorganic carbon utilized for photosynthesis in Chlorella vulgaris 11h cells
- Role of carbonic anhydrase in photosynthetic CO_2 fixation in Chlorella
- Oxygen enhancement of photosynthesis in Anacystis nidulans cells
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- Effect of Temperature on Starch Degradation in Chlorella vulgaris 11h Cells
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