Biodegradation of RDX nitroso products MNX and TNX by cytochrome P450 XpIA

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DOIResolve DOI: http://doi.org/10.1021/es3011964
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TypeArticle
Journal titleEnvironmental Science & Technology
Volume46
Issue13
Pages72457251; # of pages: 7
AbstractAnaerobic transformation of the explosive RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) by microorganisms involves sequential reduction of N-NO2 to the corresponding N-NO groups resulting in the initial formation of MNX (hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine). MNX is further reduced to the dinitroso (DNX) and trinitroso (TNX) derivatives. In this paper, we describe the degradation of MNX and TNX by the unusual cytochrome P450 XplA that mediates metabolism of RDX in Rhodococcus rhodochrous strain 11Y. XplA is known to degrade RDX under aerobic and anaerobic conditions, and, in the present study, was found able to degrade MNX to give similar products distribution including NO2-, NO3-, N2O, and HCHO but with varying stoichiometric ratio, that is, 2.06, 0.33, 0.33, 1.18, and 1.52, 0.15, 1.04, 2.06, respectively. In addition, the ring cleavage product 4-nitro-2,4,-diazabutanal (NDAB) and a trace amount of another intermediate with a [M-H]- at 102 Da, identified as ONNHCH2NHCHO (NO-NDAB), were detected mostly under aerobic conditions. Interestingly, degradation of TNX was observed only under anaerobic conditions in the presence of RDX and/or MNX. When we incubated RDX and its nitroso derivatives with XplA, we found that successive replacement of N-NO2 by N-NO slowed the removal rate of the chemicals with degradation rates in the order RDX > MNX > DNX, suggesting that denitration was mainly responsible for initiating cyclic nitroamines degradation by XplA. This study revealed that XplA preferentially cleaved the N-NO2 over the N-NO linkages, but could nevertheless degrade all three nitroso derivatives, demonstrating the potential for complete RDX removal in explosives-contaminated sites.
Publication date
LanguageEnglish
AffiliationNRC Biotechnology Research Institute; National Research Council Canada
Peer reviewedYes
NRC number53419
NPARC number20375240
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Record identifierb128ea00-7bf3-44ba-a1d9-96d16f8b2c81
Record created2012-07-26
Record modified2016-05-09
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