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Title
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Understanding the molecular basis of industrially relevant biocatalysts : an electron paramagnetic resonance investigation of chlorite dismutases
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Author
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Abstract
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| Chlorite dismutases (Clds) are heme b-containing oxidoreductases of bacterial origin which degrade chlorite to form chloride and molecular oxygen. This unique enzymatic activity was originally found in perchlorate- and chlorate-reducing bacteria, where Clds act as scavenging systems for the toxic chlorite produced during the respiration. In addition to their intriguing reactivity – the formation of an O-O bond was formerly described only for oxygenic organisms and in a methano-oxidizing bacterium – chlorite dismutases raised interest for their potential industrial applications, such as in the field of bioremediation, construction of biosensors and as a tool to improve aeration in bioreactors, to cite a few. This work is principally focused on the study of the dimeric chlorite dismutase from Cyanothece sp. PCC7425 (CCld) to gain insights into different enzyme properties, including the role of key amino acids in the heme surroundings, modes of ligand binding and mechanistic details. The integration of different approaches, including site-directed mutagenesis, structure determination, activity and stability assays, was necessary to elucidate the investigated aspects. The project can be viewed as a combination of three main research questions: i) the role(s) of a conserved arginine residue situated at the distal side of the heme iron and the impact of its flexibility on different enzyme properties; ii) the mechanism of substrate binding and the influence of the arginine in this aspect; iii) the nature of the intermediate states formed during the catalytic cycle and their dependency on pH. Exploiting the paramagnetic nature of the ferric heme iron, either in the resting state of the enzyme, or upon ligand binding and in reaction with the substrate(s), electron paramagnetic resonance (EPR) spectroscopy was chosen in this work as a principal approach to address these questions. In addition to that, preliminary experiments of enzyme immobilization in different materials were performed, with the scope of expanding the chlorite dismutase potential for industrial usages. Overall, this work aimed at gaining a comprehensive understanding of the molecular determinants of chlorite dismutases’ peculiar reactivity, using an integrative structural biology approach, where EPR spectroscopy proved to be a valuable technique to obtain information about the heme-containing active site of CCld. |
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Language
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English
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Publication
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Antwerp
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University of Antwerp, Faculty of Science
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2023
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Volume/pages
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xxv, 280 p.
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Note
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Van Doorslaer, Sabine [Supervisor]
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García-Rubio, Inés [Supervisor]
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Full text (open access)
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The publisher created published version Available from 18.10.2025
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