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Reduction of the explosive 2,4,6‐trinitrotoluene by enzymes from aquatic sediments
Author(s) -
Van Beelen Patrick,
Burris David R.
Publication year - 1995
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620141215
Subject(s) - enzyme , trinitrotoluene , chemistry , dithiothreitol , biochemistry , oxidative enzyme , organic chemistry , explosive material
Enzymes were extracted from aquatic sediments. Some of these enzymes reduced 2,4,6‐trinitrotoluene (TNT) with nicotinamide adenosine dinucleotide phosphate (NADPH) as an electron donor under aerobic conditions. The origin of these enzymes was not clear as the enzymes were extracted from a sediment containing plant roots and microorganisms. Aquatic plants were determined to be a source of TNT‐reducing enzymes. Chemical reduction was not a rate‐limiting process in the assays as the enzymatic activity was inhibited by heating or the addition of proteases. Enzymatic activity in the extracts was further characterized. Partial purifications of enzymes from the sediment extracts shows that several proteins capable of reducing TNT with NADPH were present. The enzymes did not require flavins and preferred NADPH over NADH as the electron donor. The pH optimum for the stability of the enzymes was near neutral, and the temperature optimum was in the 37 to 45°C range. Addition of dithiothreitol improved the stability of the enzymes. The enzymes reduced 2,4,6‐trinitrotoluene to 2‐amino‐4,6‐dinitrotoluene, 4‐amino‐2,6‐dinitrotoluene, 2,4‐diamino‐6‐nitrotoluene, and 2,6‐diamino‐4‐nitrotoluene under aerobic conditions with NADPH. When used as a starting substrate, the aminodinitrotoluenes were not reduced by the enzymes. It might be possible that the hydroxylaminodinitrotoluenes are reduced to di[hydroxylamine]nitrotoluenes prior to the formation of the diamino‐nitrotoluenes. Sediments from 11 surface water bodies were examined for the presence of TNT‐reducing enzymes, and 10 were found to have activity. These enzymes appear to be ubiquitous and are present in both freshwater and saltwater sediments. Reduction of TNT by sediment enzymes can be a significant environmental fate process for TNT in aquatic systems.