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Substrate and Enzyme Specificity of the Kinetic Isotope Effects Associated with the Dioxygenation of Nitroaromatic Contaminants
Eawag, Swiss Fed Inst Aquat Sci & Technol, CH-8600 Dubendorf, Switzerland.;Swiss Fed Inst Technol, Inst Biogeochem & Pollutant Dynam IBP, CH-8092 Zurich, Switzerland..
Eawag, Swiss Fed Inst Aquat Sci & Technol, CH-8600 Dubendorf, Switzerland..
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Structure and Molecular Biology. Lodz Univ Technol, Inst Appl Radiat Chem, PL-90924 Lodz, Poland..
Lodz Univ Technol, Inst Appl Radiat Chem, PL-90924 Lodz, Poland..
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2016 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 50, no 13, 6708-6716 p.Article in journal (Refereed) PublishedText
Abstract [en]

Compound-specific isotope analysis (CSIA) is a promising approach for tracking biotransformation of organic pollutants, but isotope fractionation associated with aromatic oxygenations is only poorly understood. We investigated the dioxygenation of a series of nitroaromatic compounds to the corresponding catechols by two enzymes, namely, nitrobenzene and 2-nitrotoluene dioxygenase (NBDO and 2NTDO) to elucidate the enzyme- and substrate-specificity of C and H isotope fractionation. While the apparent C-13- and H-2-kinetic isotope effects of nitrobenzene, nitrotoluene isomers, 2,6-dinitrotoluene, and naphthalene dioxygenation by NBDO varied considerably, the correlation of C and H isotope fractionation revealed a common mechanism for nitrobenzene and nitrotoluenes. Similar observations were made for the dioxygenation of these substrates by 2NTDO. Evaluation of reaction kinetics, isotope effects, and commitment-to-catalysis based on experiment and theory showed that rates of dioxygenation are determined by the enzymatic O-2 activation and aromatic C oxygenation. The contribution of enzymatic O-2 activation to the reaction rate varies for different nitroaromatic substrates of NBDO and 2NTDO. Because aromatic dioxygenation by nonheme iron dioxygenases is frequently the initial step of biodegradation, O-2 activation kinetics may also have been responsible for the minor isotope fractionation reported for the oxygenation of other aromatic contaminants.

Place, publisher, year, edition, pages
2016. Vol. 50, no 13, 6708-6716 p.
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URN: urn:nbn:se:uu:diva-300468DOI: 10.1021/acs.est.5b05084ISI: 000379366300016PubMedID: 26895026OAI: oai:DiVA.org:uu-300468DiVA: diva2:951447
Available from: 2016-08-09 Created: 2016-08-09 Last updated: 2016-08-09Bibliographically approved

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