Toluene 4-monooxygenase

NATASA Mine, GERHARD SCHENK and GRAEME R. HANSON 

Toluene/o-xylene (ToMO) from P. stutzeri 0X1, which has recently been expressed and purified, belongs to a class of bacterial multicomponent monooxygenases, and is also closely related to MMO [11,12,207]. It catalyzes the oxidation 

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Toluene monooxygenases provide alternatives to dioxygenation, and the ortho-mono-oxygenase in Burkholderia (Pseudomonas) cepacia G4 has been shown to be carried... 

Although monooxygenases can be involved in the degradation of toluene, there is a complex relation between toluene monooxygenase activity and the degradation of chlorinated hydrocarbons. 

Degradation of toluene may also take place in different species of Pseudomonas by initial monooxygenation at the 2-, 3-, or 4-positions. The situation for toluene monooxygenases has been confusing. However, it is now recognized that only the following two initial reactions take place ... 

Carbon isotope fractionation was examined during the aerobic degradation of TCE by Burkholderia cepacia strain G4 that possesses toluene monooxygenase activity (Barth et al. 2002). There were substantial differences in values of isotope shifts during degradation, from 57 to 17 ppm, and when the data were corrected to correspond to the same amount of substrate reduction the Releigh enrichment factor was 18.2. 

Nolan, L.C. and O Connor, K.E., Use of Pseudomonas mendocina, or recombinant Escherichia coli cells expressing toluene -monooxygenase, and a cell-free tyrosinase for the synthesis of 4-fluorocatechol from fluorobenzene. Biotechnol. Lett., 2007, 29, 1045. 

Tugusheva, M. Steffen, R.J. (1993). In vitro construction of constitutive toluene monooxygenase (TMO) mutants of Pseudomonas mendocina KR1. In Abstract, 93rd Annual Meeting of the American Society for Microbiology, abstr. K-89, p- 276. Washington, DC The American Society for Microbiology. 

K. McClay, B. G. Fox, R. J. Steffan, Toluene monooxygenase-catalyzed epoxidation of alkenes, Appl. Environ. Microbiol. 66 (2000) 1877. 

Monooxygenase systems are sometimes involved in the degradation of toluene (Section 6.2.1) and plausibly in the transformation of aromatic compounds to arene oxide intermediates (Chapter 4, Sections 4.2.3 and 4.4.1.1, and in Sections 6.2.2 and 6.3.1.2). There is a complex relation between toluene monooxygenase activity and the degradation of chlorinated hydrocarbons. 

Scheme 2 Benzylic hydroxylation and aromatic cw-dihydroxylation reactions catalyzed by Rieske oxygenases (toluene monooxygenase and naphthalene-1,2-dioxygenase, respectively)...

Figure 3. Biotransformation of nitrotoluene by toluene monooxygenase, produced by the TOL plasmid pWWO...

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