Characterization of a Gene Cluster Involved in 4-Chlorocatechol Degradation by Pseudomonas reinekei MT1

Department of Microbial Pathogenesis, HZI Helmholtz Centre for Infection Research, Braunschweig, Germany.
Journal of bacteriology (Impact Factor: 2.81). 06/2009; 191(15):4905-15. DOI: 10.1128/JB.00331-09
Source: PubMed


Pseudomonas reinekei MT1 has previously been reported to degrade 4- and 5-chlorosalicylate by a pathway with 4-chlorocatechol, 3-chloromuconate,
4-chloromuconolactone, and maleylacetate as intermediates, and a gene cluster channeling various salicylates into an intradiol
cleavage route has been reported. We now report that during growth on 5-chlorosalicylate, besides a novel (chloro)catechol
1,2-dioxygenase, C12OccaA, a novel (chloro)muconate cycloisomerase, MCIccaB, which showed features not yet reported, was induced. This cycloisomerase, which was practically inactive with muconate,
evolved for the turnover of 3-substituted muconates and transforms 3-chloromuconate into equal amounts of cis-dienelactone and protoanemonin, suggesting that it is a functional intermediate between chloromuconate cycloisomerases and
muconate cycloisomerases. The corresponding genes, ccaA (C12OccaA) and ccaB (MCIccaB), were located in a 5.1-kb genomic region clustered with genes encoding trans-dienelactone hydrolase (ccaC) and maleylacetate reductase (ccaD) and a putative regulatory gene, ccaR, homologous to regulators of the IclR-type family. Thus, this region includes genes sufficient to enable MT1 to transform
4-chlorocatechol to 3-oxoadipate. Phylogenetic analysis showed that C12OccaA and MCIccaB are only distantly related to previously described catechol 1,2-dioxygenases and muconate cycloisomerases. Kinetic analysis
indicated that MCIccaB and the previously identified C12OsalD, rather than C12OccaA, are crucial for 5-chlorosalicylate degradation. Thus, MT1 uses enzymes encoded by a completely novel gene cluster for degradation
of chlorosalicylates, which, together with a gene cluster encoding enzymes for channeling salicylates into the ortho-cleavage pathway, form an effective pathway for 4- and 5-chlorosalicylate mineralization.

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    • "The genes cphC-I and cphC-II encode putative monooxygenase, whereas cphF-1 and cphF-11 encode putative maleylacetate reductase and cphB encodes a NADH:flavin adenine dinucleotide oxidoreductase. The roles of the remaining genes in the cph gene cluster have yet to be determined [112]. "
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    • "Hollender et al. (1997) reported the degradation of 4-chlorophenol via the formation of 4-chlorocatechol. Literature studies showed that 4- chlorocatechol was degraded either via the ortho -cleavage pathway or the meta-cleavage pathway (Cámara et al. 2009; Nikodem et al. 2003; Hollender et al. 1997). In the orthocleavage pathway, 4-chlorocatechol was cleaved into 3- chloro-cis ,cis -muconate by a 4-chlorocatechol-1,2-doixy- genase (Nikodem et al. 2003). "
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    • "Enhanced degradation avoids accumulation of toxic metabolic intermediates such as catechols [5], [39]. The toxicity of aromatic compounds and their metabolic intermediates for strain LB400 has been reported [9], [31], [35]. "
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