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Exploring the biochemical properties and remediation applications of the unusual explosive-degrading P450 system XplA/B

Jackson, R.G., Rylott, E.L., Fournier, D., Hawari, J. and Bruce, N.C. (2007) Exploring the biochemical properties and remediation applications of the unusual explosive-degrading P450 system XplA/B. Proceedings of the National Academy of Science, USA, 104 (43). pp. 16822-16827. ISSN 0027-8424

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Abstract

Widespread contamination of land and groundwater has resulted from the use, manufacture, and storage of the military explosive hexa-hydro-1,3,5-trinitro-1,3,5-triazine (RDX). This contamination has led to a requirement for a sustainable, low-cost method to remediate this problem. Here, we present the characterization of an unusual microbial P450 system able to degrade RDX, consisting of flavodoxin reductase XplB and fused flavodoxin-cytochrome P450 XplA. The affinity of XplA for the xenobiotic compound RDX is high (K d = 58 μM) and comparable with the K m of other P450s toward their natural substrates (ranging from 1 to 500 μM). The maximum turnover (k cat) is 4.44 per s, only 10-fold less than the fastest self-sufficient P450 reported, BM3. Interestingly, the presence of oxygen determines the final products of RDX degradation, demonstrating that the degradation chemistry is flexible, but both pathways result in ring cleavage and release of nitrite. Carbon monoxide inhibition is weak and yet the nitroaromatic explosive 2,4,6-trinitrotoluene (TNT) is a potent inhibitor. To test the efficacy of this system for the remediation of groundwater, transgenic Arabidopsis plants expressing both xplA and xplB were generated. They are able to remove saturating levels of RDX from liquid culture and soil leachate at rates significantly faster than those of untransformed plants and xplA-only transgenic lines, demonstrating the applicability of this system for the phytoremediation of RDX-contaminated sites.

Item Type: Article
Academic Units: The University of York > Biology (York)
Depositing User: York RAE Import
Date Deposited: 20 Feb 2009 12:21
Last Modified: 20 Feb 2009 12:21
Published Version: http://dx.doi.org/10.1073/pnas.0705110104
Status: Published
Publisher: National Academy of Sciences
Identification Number: 10.1073/pnas.0705110104
URI: http://eprints.whiterose.ac.uk/id/eprint/7329

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