Carbon dioxide fixation by isolated chloroplasts of Euglena gracilis. I. Isolation of functionally intact chloroplasts and their characterization |
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| Authors: | W T Forsee J S Kahn |
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| Affiliation: | 1. State Key Laboratory of Cryosphere Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Science, Lanzhou 73000, China;2. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China;3. Key laboratory of Western China''s Environmental System (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China;4. Institute for Atmospheric and Climate Science, ETH Zurich, CH-8092 Zurich, Switzerland;5. Laboratory of Green Chemistry, Lappeenranta University of Technology, Mikkeli 50130, Finland;6. Unviersity of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | A method was developed for isolating functionally intact chloroplasts from heterotrophically grown Euglena. These isolated chloroplasts are capable of fixing CO2 at rates up to 30 μmoles/mg chlorophyll/hr, which is one-half the rate of the whole cells. In contrast to chloroplasts isolated from spinach, Euglena chloroplasts are strongly inhibited by the presence of sucrose or by isolation at low pH. ATP is not able to reverse the inhibition of CO2 fixation by uncouplers of photophosphorylation, indicating that the chloroplast envelope is not permeable to ATP. Pyrophosphate stimulates CO2 fixation only in the absence of inorganic phosphate. The presence of inorganic phosphate causes a lag period before maximum rates of CO2 fixation are achieved, and this lag is diminished by the addition of 3-phosphoglycerate and ribose-5-phosphate. Pyocyanin inhibits CO2 fixation, and the addition of ribose-5-phosphate fails to reverse this inhibition. |
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