PHOTOINACTIVATION OF A Chlamydomonas MUTANT(NL–11) IN THE PRESENCE OF METHIONINE: ROLES OF H2O2 and O-2 |
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| Authors: | Umeo Takahama Takeshi Egashira Kazuo Nakamura |
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| Institution: | Department of Biology, Kyushu Dental College, Kitakyushu 803, Japan;department of Biological Sciences, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada T1K 3M4 |
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| Abstract: | Abstract— A mutant of Chlamydomonas reinhardtii (NL–11) isolated from a wild type (137c+) was inactivated in the light in the presence of methionine at concentrations where the wild type was not inactivated. The inactivation was suppressed by either catalase or superoxide dismutase (SOD). Light-induced H2O2 formation and nitroblue tetrazolium (NBT) reduction inNL–11 were greater than those in the wild type. Methionine stimulated both the H2O2 formation and the NBT reduction inNL–11 as well as the wild type. The light-induced NBT reduction inNL–11 in the presence of methionine was partially suppressed by externally added SOD suggesting the participation of O-2. These results suggest that the hypersensitivity ofNL–11 to methionine in the light is due to stimulated formation of H2O2 and O-2. |
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