This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Aromatic Compounds Degradation → Chloroaromatic Compounds Degradation → Chlorocatechol Degradation|
|Degradation/Utilization/Assimilation → Chlorinated Compounds Degradation → Chloroaromatic Compounds Degradation → Chlorocatechol Degradation|
Expected Taxonomic Range: Bacteria
Chloroaromatic compounds occur in the environment in large amounts due to their release as herbicides or as byproducts of industrial production. These compounds are stable chemically, and biological degradation capabilities have evolved only recently as a response to their widespread availability in soil and water.
Many of the degradation pathways merge at the level of chlorocatechols.Often organisms that can degrade non-chlorinated aromatic compounds (such as benzoate) can convert the chlorinated vatiants to the level of chlorocatechols, due to enzyme promiscuity [Spokes74]. However, the enzymes that degrade catechol have little activity with chloro-substituted compounds, and the chlorocatechols that accumulate as a result are toxic to the bacteria. Thus, in order to be able to degrade chlorobenzoates and chlorobenzenes successfully, the bacteria must possess specific enzymes for the degradation of chlorocatechols.
The first bacterium that was isolated based on its ability to grow with 3-chlorobenzoate as the sole carbon source was Pseudomonas knackmussii (then called Pseudomonas sp. strain B13) [Dorn74]. That study showed that 3-chlorobenzoate was converted by two enzymes to a mixture of 3-chlorocatechol and 4-chlorocatechol [Dorn74, Weisshaar87]. The chlorinated catechols were degraded in a modified ortho cleavage pathways via 2-maleylacetate to 3-oxoadipate, which was degraded further to TCA cycle intermediates.
This pathway for 4-chlorocatechol degradation starts with a dioxygenase attack, resulting in 3-chloro-cis,cis-muconate. The "regular" catechol 1,2 dioxygenases have little activity with chlorocatechol. Instead, chlorocatechols are substrates to specialized enzymes that evolved for this purpose, known as "type II" enzymes. The next enzyme, chloromuconate cycloisomerase, catalyzes a single reaction that converts the chloromuconate directly to cis-dienelactone [Kaulmann01]. The reaction includes the removal of the chloride residue. Two last steps, catalyzed by a hydrolase and a reductase, generate the common intermediate 3-oxoadipate.
Most of the genes encoding chlorocatechol catabolism enzymes are present on plasmids. Examples include the two tdf operons on the Ralstonia eutropha JMP134 plasmid pJP4 [Don85], the clc operon on the Pseudomonas knackmussii plasmid pB13 (pWR1) [Chatterjee81], and the tcb operon on the Pseudomonas sp. P51 plasmid pP51 [vanderMeer91].
In bacteria that lack chloromuconate cycloisomerase formation of 4-chlorocatechol leads to accute toxicity. Apparently 3-chloro-cis,cis-muconate can be converted by the regular, chromosomally-encoded muconate cycloisomerase to the toxic antibiotic protoanemonin via the following reactions:
Blasco95: Blasco R, Wittich RM, Mallavarapu M, Timmis KN, Pieper DH (1995). "From xenobiotic to antibiotic, formation of protoanemonin from 4-chlorocatechol by enzymes of the 3-oxoadipate pathway." J Biol Chem 270(49);29229-35. PMID: 7493952
Chatterjee81: Chatterjee DK, Kellogg ST, Hamada S, Chakrabarty AM (1981). "Plasmid specifying total degradation of 3-chlorobenzoate by a modified ortho pathway." J Bacteriol 146(2);639-46. PMID: 7217013
Don85: Don RH, Weightman AJ, Knackmuss HJ, Timmis KN (1985). "Transposon mutagenesis and cloning analysis of the pathways for degradation of 2,4-dichlorophenoxyacetic acid and 3-chlorobenzoate in Alcaligenes eutrophus JMP134(pJP4)." J Bacteriol 161(1);85-90. PMID: 2981813
Gaillard06: Gaillard M, Vallaeys T, Vorholter FJ, Minoia M, Werlen C, Sentchilo V, Puhler A, van der Meer JR (2006). "The clc element of Pseudomonas sp. strain B13, a genomic island with various catabolic properties." J Bacteriol 188(5);1999-2013. PMID: 16484212
Kaulmann01: Kaulmann U, Kaschabek SR, Schlomann M (2001). "Mechanism of chloride elimination from 3-chloro- and 2,4-dichloro-cis,cis-muconate: new insight obtained from analysis of muconate cycloisomerase variant CatB-K169A." J Bacteriol 183(15);4551-61. PMID: 11443090
vanderMeer91: van der Meer JR, van Neerven AR, de Vries EJ, de Vos WM, Zehnder AJ (1991). "Cloning and characterization of plasmid-encoded genes for the degradation of 1,2-dichloro-, 1,4-dichloro-, and 1,2,4-trichlorobenzene of Pseudomonas sp. strain P51." J Bacteriol 173(1);6-15. PMID: 1987135
Weisshaar87: Weisshaar MP, Franklin FC, Reineke W (1987). "Molecular cloning and expression of the 3-chlorobenzoate-degrading genes from Pseudomonas sp. strain B13." J Bacteriol 169(1);394-402. PMID: 3025183
Broderick91: Broderick JB, O'Halloran TV (1991). "Overproduction, purification, and characterization of chlorocatechol dioxygenase, a non-heme iron dioxygenase with broad substrate tolerance." Biochemistry 30(29);7349-58. PMID: 1649626
Camara07: Camara B, Bielecki P, Kaminski F, dos Santos VM, Plumeier I, Nikodem P, Pieper DH (2007). "A gene cluster involved in degradation of substituted salicylates via ortho cleavage in Pseudomonas sp. strain MT1 encodes enzymes specifically adapted for transformation of 4-methylcatechol and 3-methylmuconate." J Bacteriol 189(5);1664-74. PMID: 17172348
Daubaras96: Daubaras DL, Saido K, Chakrabarty AM (1996). "Purification of hydroxyquinol 1,2-dioxygenase and maleylacetate reductase: the lower pathway of 2,4,5-trichlorophenoxyacetic acid metabolism by Burkholderia cepacia AC1100." Appl Environ Microbiol 62(11);4276-9. PMID: 8900023
Endo05: Endo R, Kamakura M, Miyauchi K, Fukuda M, Ohtsubo Y, Tsuda M, Nagata Y (2005). "Identification and characterization of genes involved in the downstream degradation pathway of gamma-hexachlorocyclohexane in Sphingomonas paucimobilis UT26." J Bacteriol 187(3);847-53. PMID: 15659662
Frantz87: Frantz B, Chakrabarty AM (1987). "Organization and nucleotide sequence determination of a gene cluster involved in 3-chlorocatechol degradation." Proc Natl Acad Sci U S A 84(13);4460-4. PMID: 3299368
Frantz87a: Frantz B, Ngai KL, Chatterjee DK, Ornston LN, Chakrabarty AM (1987). "Nucleotide sequence and expression of clcD, a plasmid-borne dienelactone hydrolase gene from Pseudomonas sp. strain B13." J Bacteriol 169(2);704-9. PMID: 3804974
Halak07: Halak S, Basta T, Burger S, Contzen M, Wray V, Pieper DH, Stolz A (2007). "4-sulfomuconolactone hydrolases from Hydrogenophaga intermedia S1 and Agrobacterium radiobacter S2." J Bacteriol 189(19);6998-7006. PMID: 17660282
Kasberg95: Kasberg T, Daubaras DL, Chakrabarty AM, Kinzelt D, Reineke W (1995). "Evidence that operons tcb, tfd, and clc encode maleylacetate reductase, the fourth enzyme of the modified ortho pathway." J Bacteriol 177(13);3885-9. PMID: 7601858
Kasberg97: Kasberg T, Seibert V, Schlomann M, Reineke W (1997). "Cloning, characterization, and sequence analysis of the clcE gene encoding the maleylacetate reductase of Pseudomonas sp. strain B13." J Bacteriol 179(11);3801-3. PMID: 9171435
Kaschabek92: Kaschabek SR, Reineke W (1992). "Maleylacetate reductase of Pseudomonas sp. strain B13: dechlorination of chloromaleylacetates, metabolites in the degradation of chloroaromatic compounds." Arch Microbiol 158(6);412-7. PMID: 1482270
Kaschabek93: Kaschabek SR, Reineke W (1993). "Degradation of chloroaromatics: purification and characterization of maleylacetate reductase from Pseudomonas sp. strain B13." J Bacteriol 175(19);6075-81. PMID: 8407778
Kuhm90: Kuhm AE, Schlomann M, Knackmuss HJ, Pieper DH (1990). "Purification and characterization of dichloromuconate cycloisomerase from Alcaligenes eutrophus JMP 134." Biochem J 266(3);877-83. PMID: 2327971
Laemmli02: Laemmli CM, Schonenberger R, Suter M, Zehnder AJ, van der Meer JR (2002). "TfdD(II), one of the two chloromuconate cycloisomerases of Ralstonia eutropha JMP134 (pJP4), cannot efficiently convert 2-chloro- cis, cis-muconate to trans-dienelactone to allow growth on 3-chlorobenzoate." Arch Microbiol 178(1);13-25. PMID: 12070765
Matus03: Matus V, Sanchez MA, Martinez M, Gonzalez B (2003). "Efficient degradation of 2,4,6-Trichlorophenol requires a set of catabolic genes related to tcp genes from Ralstonia eutropha JMP134(pJP4)." Appl Environ Microbiol 69(12);7108-15. PMID: 14660355
Moiseeva01: Moiseeva OV, Belova OV, Solyanikova IP, Schlomann M, Golovleva LA (2001). "Enzymes of a new modified ortho-pathway utilizing 2-chlorophenol in Rhodococcus opacus 1CP." Biochemistry (Mosc) 66(5);548-55. PMID: 11405892
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