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Two-electron reduction of nitroaromatic compounds by Thermotoga maritima hybrid peroxiredoxin-nitroreductase enzyme
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Edité par CCSD ; Publishing Department of the Lithuanian Academy of Sciences -
International audience. Explosives such as 2,4,6-trinitrotoluene (TNT) and related polynitroaromatics being toxic environmental pollutants, numerous efforts are directed towards their biodegradation. In this work, we studied the NADPH-dependent two-electron reduction of a number of nitroaromatic compounds by a peroxiredoxin-nitroreductase hybrid enzyme from Thermotoga maritima (Prx-NR). We have found that the peroxiredoxin and nitroreductase domains of Prx-NR function independently. The activity of Prx-NR towards nitroaromatics is not influenced by their particular structure and is characterized by a linear log k(cat)/K(m) dependence on their single-electron reduction potentials (E(7)(1)). The reduction of polynitroaromatic explosives N-nitramines such as tetryl (2,4,6-trinitrophenyl-N-methylnitramine) and pentryl (2,4,6-trinitrophenyl-N-nitroaminoethylnitrate) was accompanied by the formation of nitrite, which implies their reductive N-denitration, while p-dinitrobenzene is reduced to p-hydroxylaminonitrobenzene. Taken together, these data indicate that nitroreductase reactions of Prx-NR share common features with those of other bacterial oxygen-insensitive nitroreductases, e. g., Enterobacter cloacae nitroreductase. However, the activity of Prx-NR is 10-100 times lower than that of E. cloacae NR.
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