Authors: HyounYoung Kim HongGyu Song
Publish Date: 2005/03/24
Volume: 68, Issue: 6, Pages: 766-773
Abstract
Three NADPHdependent nitroreductases that can transform 246trinitrotoluene TNT by two reduction pathways were detected in Klebsiella sp C1 Among these enzymes the protein with the highest reduction activity of TNT nitroreductase I was purified to homogeneity using ionexchange hydrophobic interaction and size exclusion chromatographies Nitroreductase I has a molecular mass of 27 kDa as determined by SDSPAGE and exhibits a broad pH optimum between 55 and 65 with a temperature optimum of 30–40°C Flavin mononucleotide is most likely the natural flavin cofactor of this enzyme The Nterminal amino acid sequence of this enzyme does not show a high degree of sequence similarity with nitroreductases from other enteric bacteria This enzyme catalyzed the twoelectron reduction of several nitroaromatic compounds with very high specific activities of NADPH oxidation In the enzymatic transformation of TNT 2amino46dinitrotoluene and 22′66′tetranitro44′azoxytoluene were detected as transformation products Although this bacterium utilizes the direct ring reduction and subsequent denitration pathway together with a nitro group reduction pathway metabolites in direct ring reduction of TNT could not easily be detected Unlike other nitroreductases nitroreductase I was able to transform hydroxylaminodinitrotoluenes HADNT into aminodinitrotoluenes ADNT and could reduce ortho isomers 2HADNT and 2ADNT more easily than their para isomers 4HADNT and 4ADNT Only the nitro group in the ortho position of 24DNT was reduced to produce 2hydroxylamino4nitrotoluene by nitroreductase I the nitro group in the para position was not reduced
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