2-nitrotoluene-2,3-dioxygenase

Parales JV, RE Parales, SM Resnick, DT Gibson (1998) Enzyme specificity of 2-nitrotoluene 2,3-dioxygenase from Pseudomonas sp. strain JS42 is determined by the C-terminal region of the a subunit of the oxygenase component. / Sacfeno/ 180 1194-1199. 

Robertson JB, JC Spain, JD Haddock, DT Gibson (1992) Oxidation of nitrotoluenes by toluene dioxygenase evidence for a monooxygenase reaction. Appl Environ Microbiol 58 2643-2648. 

Biological. Under anaerobic conditions using a sewage inoculum, 3-nitrotoluene and 4-nitrotoluene both degraded to toluidine (Hallas and Alexander, 1983). Robertson et al. (1992) reported that toluene dioxygenases from Pseudomonas putida FI and Pseudomonas sp. Strain JS 150 oxidized the methyl group forming 3-nitrobenzyl alcohol. 

The biotransformation of nitrotoluenes has been examined in toluene-grown cells of pseudomonads which contain a toluene dioxygenase. The products depended on the relative position of the substituents and clearly illustrated the various metabolic reactions that may be mediated by this dioxygenase 2-nitro- and 3-nitrotol-uene were converted into the corresponding benzyl alcohols, whereas 4-nitrotoluene produced 3-methyl-6-nitrocatechol and 2-methyl-5-nitrophenol (Figure 6.113) (Robertson et al. 1992). 

Arene dioxygenases catalyze the first step in the metabolism of unactivated aromatic compounds, yielding cw-dihydrodiol of aromatics. As shown in eq. (22), the reaction requires nicotinamide adenine nucleotide (NADH) and molecular oxygen. Substrate specificity of enzymes is high, and products shown in Fig. 27 are produced by benzene-[351, 352], toluene- [353-356], naphthalene- [357-361], biphenyl- [362-364], benzoate-[365-370], and phthalate-dioxygenases [371-378]. In the cases of benzoate [379], 4-sulphobenzoate [380], and 6>-nitrotoluene [381], catechols are formed via unstable dihydroxylated intermediates as shown in eq. (23)... 

Dinitro toluene dioxygenase Burkholderia sp. DNT Saturation mutagenesis 1204Y/L 1204Y Increased activities against 2-nitrotoluene and 2,4- and 2,6-dinitrotoluene new activity against 2,3- and 2,5-dinitro toluene Increased oxidation rate of aminonitrotoluenes [26] [27]... 

Residue 293 is located at a hydrophobic cleft on the surface of nitrobenzene dioxygenase that mediates aromatic substrate binding. The specificity of enzymes with substitutions at position 293 varied depending on the residue present as well as the substrate [29]. For example, F293H/Q/1 substitutions in the alpha subunit of nitrobenzene dioxygenase did not cause any significant changes in the ratios of products formed from 3-nitrotoluene (3-methylcatechol, 4-methylcatechol, and... 

Microbial metabolism of 2- and 3-nitrotoluene seems to be more difficult than metabolism of 4-nitrotoluene. However, a variety of mechanisms are known for the initial attack on unsubstituted toluene by bacteria (Fig. 2). Strains that contain the TOL plasmid oxidized the methyl group to the corresponding alcohol, aldehyde and carboxylic acid derivatives (55). Pseudomonasputida FI and similar strains produce a toluene dioxygenase that initially attacks at the 2,3- position on the ring. This yields a cw-dihydrodiol that is then... 

Figure 4. Biotransformation of toluene and nitrotoluenes by the chromosomally encoded toluene dioxygenase of Pseudomonas sp. FI.

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