Chlorocatechols

CHLOROBENZENE Total 4-chlorocatechol in urine End of shift 1 50 mg/g creatinine Ns... 

The degradation of 4-chlorobiphenyl by Sphingomonas paucimobilis strain BPSl-3 formed the intermediates 4-chlorobenzoate and 4-chlorocatechol. Fission products from the catechol reacted with NH4+ to produce chloropyridine carboxylates (Davison et al. 1996) (Figure 2.2c). 

Kaschabek SR, T Kasberg, D Muller, AE Mars, DB Janssen, W Reineke (1998) Degradation of chloroaromat-ics purification and characterization of a novel type of chlorocatechol 2,3-dioxygenase of Pseudomonas putida GJ31. J Bacterial 180 296-302. 

Experiments examined a chlorocatechol-contaminated sediment, and interstitial water prepared from it. These showed that the concentrations of total 3,4,5-tri- and tetrachloro-catechols (i.e., including the fraction that is released only after alkaline extraction) were apparently unaltered during prolonged incubation even after addition of cnltnres with established dechlorinating capability for the soluble chlorocatechols (Allard et al. 1994). 

C subfamily of type 1 extradiol dioxygenases (Mars et al. 1999). The alternative extradiol fission of 3-chlorocatechol may take place between the 1 and 6 positions (distal fission), and this has been shown for the 2,3-dihydroxybiphenyl 1,2-dioxygenase from the naphthalene sulfonate degrading Sphingomonas sp. strain BN6 (Riegert et al. 1998). 

Allard A-S, P-A Hynning, C Lindgren, M Remberger, AH Neilson (1991) Dechlorination of chlorocatechols by stable enrichment cultures of anaerobic bacteria. Appl Environ Microbiol 57 7784. 

Blasco R, R-M Wittich, M Mallavarapu, KN Timmis, DH Pieper (1995) From xenobiotic to antibiotic, formation of protoanemonin from 4-chlorocatechol by enzymes of the 3-oxoadipate pathway. J Biol Chem 270 29229-29235. 

Frantz B, AM Chakrabarty (1987) Organization and nucleotide sequence determination of a gene cluster involved in 3-chlorocatechol degradation. Proc Natl Acad Sci USA 84 4460-4464. 

Mars AE, J Kingma, SR Kaschabek, W Reinke, DB Janssen (1999) Conversion of 3-chlorocatechol by various catechol 2,3-dioxygenases and sequence analysis of the chlorocatechol dioxygense region of Pseudomonas putida GJ31. J Bacterial 181 1309-1318. 

Riegert U, G Heiss, P Fischer, A Stolz (1998) Distal cleavage of 3-chlorocatechol by an extradiol dioxygenase to 3-chloro-2-hydroxymuconic semialdehyde. J Bacterial 180 2849-2853. 

The extensive use in a series of experiments on the anaerobic dechlorination of chlorocatechols (references in Allard et al. 1994). 

Additional limitations. Other limitations have been enconntered (a) the formation of the inhibitory protoanemonin from 4-chlorocatechols (Blasco et al. 1995) and (b) the ineffectiveness of cycloisomerases reqnired for effective degradation of 2-chlorotoluene (Polhnann et al. 2005). An example of this limitation is given later, and in the degradation of 3-flnorobenzoate in Part 3 of this chapter. 

FIGURE 9.12 Ring-cleavage pathways for the biodegradation of chlorocatechols formed from 3- and 4-chlorobenzoates. 

It is convenient to provide a short introduction to the issues encountered in the degradation of chlorinated substrates that produce chlorocatechols as intermediates. An outline of the ring-fission mechanisms has been given in Chapter 3, Part 1, and Chapter 8, Part 3. Three pathways for fission... 

Dioxygenation with decarboxylation bnt withont loss of halogen to prodnce chlorocatechols that may be degraded by several ring-fission pathways (3- and 4-chlorobenzoates) Dioxygenation with loss of only halogen to prodnce a dihydroxybenzoate (2-chlorobenzoate)... 

There is an additional problem that has important implications for the bioremediation of contaminated sites when two substrates such as a chlorinated and an alkylated aromatic compound are present. The extradiol fission pathway is generally preferred for the degradation of alkylbenzenes (Figure 9.17), although this may be incompatible with the degradation of chlorinated aromatic compounds since the 3-chlorocatechol produced inhibits the activity of the catechol-2,3-oxygenase (Klecka and Gibson 1981 Bartels et al. 1984). 

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