Characterization of Mg-dechelating substance in senescent and pre-senescent Arabidopsis thaliana leaves
The removal of Mg<sup>2+</sup> is an important step in the chlorophyll degradation pathway and extracts from senescent and presenescent <i>Arabidopsis thaliana</i> leaves were analyzed for Mg-dechelatase activity, using chlorophyllin, an artificial derivative of the natural s...
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| Autores principales: | , , |
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| Formato: | Articulo |
| Lenguaje: | Español |
| Publicado: |
2011
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| Materias: | |
| Acceso en línea: | http://sedici.unlp.edu.ar/handle/10915/133524 |
| Aporte de: |
| Sumario: | The removal of Mg<sup>2+</sup> is an important step in the chlorophyll degradation pathway and extracts from senescent and presenescent <i>Arabidopsis thaliana</i> leaves were analyzed for Mg-dechelatase activity, using chlorophyllin, an artificial derivative of the natural substrate, chlorophyllide. The optimum temperature and pH for this reaction were determined to be at approximately 50 °C and 7.2, respectively. Mg-dechelatase activity was enhanced by addition of EDTA and inhibited by MgCl<sub>2</sub>, HgCl<sub>2</sub> and reduced glutathione, indicating phenomenons such as retroinhibition by reaction products and dependence on the redox state of the mixture. Size exclusion chromatography was performed on <i>Arabidopsis</i> leaf extracts, and Mg-dechelatase activity was found in the fraction corresponding to molecular mass of about 42 kDa, which indicates that the Mg-dechelating compound in <i>Arabidopsis</i> is considerably larger than in other systems. During dark-induced senescence, the activity increased over time until reaching a maximum at day 4, and then decreased. The addition of plant growth regulators indicated that the accumulation of Mg-dechelatase was activated by ethylene and delayed by 6-benzylaminopurine. |
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