Journal of Microbiology

Research Support, Non-U.S. Gov't

Nitroreductase II Involved in 2,4,6-Trinitrotoluene Degradation: Purification and Characterization from Klebsiella sp. C1: Jung-Hye Shin , Hong-Gyu Song; J. Microbiol. 2009;47(5):536-541. Published online October 24, 2009; DOI: https://doi.org/10.1007/s12275-008-0171-6

Abstract: Three 2,4,6-trinitrotoluene (TNT) nitroreductases from Klebsiella sp. C1 have different reduction capabilities that can degrade TNT by simultaneous utilization of two initial reduction pathways. Of these, nitroreductase II was purified to homogeneity by sequential chromatographies. Nitroreductase II is an oxygen- insensitive enzyme and reduces both TNT and nitroblue tetrazolium. The N-terminal amino acid sequence of the enzyme did not show any sequence similarity with those of other nitroreductases reported. However, it transformed TNT by the reduction of nitro groups like nitroreductase I. It had a higher substrate affinity and specific activity for TNT reduction than other nitroreductases, and it showed a higher oxidation rate of NADPH with the ortho-substituted isomers of TNT metabolites (2-hydroxylaminodinitrotoluene and 2-aminodinitrotoluene) than with para-substituted compounds (4-hydroxylaminodinitrotoluene and 4-aminodinitrotoluene).

Simultaneous Utilization of Two Different Pathways in Degradation of 2,4,6-Trinitrotoluene by White Rot Fungus Irpex lacteus: Hyoun-Young Kim , Hong-Gyu Song; J. Microbiol. 2000;38(4):250-254.

Abstract: This study confirmed that white rot fungus Irpex lacteus was able to metabolize 2,4,6-trinitrotoluene (TNT) with two different initial transformations. In one metabolic pathway of TNT a nitro group was removed from the aromatic ring of TNT. Hydride-Meisenheimer complexes of TNT (H^- -TNT), colored dark red, were confirmed as the intermediate in this transformation by comparison with the synthetic compounds. 2,4-Dinitrotoluene as a following metabolic product was detected, and nitrite produced by denitration of H^- -TNT supported this transformation. In the other TNT pathway, nitro groups in TNT were successively reduced to amine groups via hydroxylamines. Hydroxylamino-dinitrotoluenes and amino-dinitrotoluenes were identified as the intermediates. The activity of a membrane-associated aromatic nitroreductase was detected in the cell-free extract of I. lacteus. This enzyme catalyzed the nitro group reduction of TNT with NADPH as a cofactor. Enzyme activity was not observed in the presence of molecular oxygen.

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