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. 2014 Jul;80(13):3811-8.
doi: 10.1128/AEM.00208-14. Epub 2014 Apr 18.

A Novel Angular Dioxygenase Gene Cluster Encoding 3-phenoxybenzoate 1',2'-dioxygenase in Sphingobium Wenxiniae JZ-1

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A Novel Angular Dioxygenase Gene Cluster Encoding 3-phenoxybenzoate 1',2'-dioxygenase in Sphingobium Wenxiniae JZ-1

Chenghong Wang et al. Appl Environ Microbiol. .
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Abstract

Sphingobium wenxiniae JZ-1 utilizes a wide range of pyrethroids and their metabolic product, 3-phenoxybenzoate, as sources of carbon and energy. A mutant JZ-1 strain, MJZ-1, defective in the degradation of 3-phenoxybenzoate was obtained by successive streaking on LB agar. Comparison of the draft genomes of strains JZ-1 and MJZ-1 revealed that a 29,366-bp DNA fragment containing a putative angular dioxygenase gene cluster (pbaA1A2B) is missing in strain MJZ-1. PbaA1, PbaA2, and PbaB share 65%, 52%, and 10% identity with the corresponding α and β subunits and the ferredoxin component of dioxin dioxygenase from Sphingomonas wittichii RW1, respectively. Complementation of pbaA1A2B in strain MJZ-1 resulted in the active 3-phenoxybenzoate 1',2'-dioxygenase, but the enzyme activity in Escherichia coli was achieved only through the coexpression of pbaA1A2B and a glutathione reductase (GR)-type reductase gene, pbaC, indicating that the 3-phenoxybenzoate 1',2'-dioxygenase belongs to a type IV Rieske non-heme iron aromatic ring-hydroxylating oxygenase system consisting of a hetero-oligomeric oxygenase, a [2Fe-2S]-type ferredoxin, and a GR-type reductase. The pbaC gene is not located in the immediate vicinity of pbaA1A2B. 3-Phenoxybenzoate 1',2'-dioxygenase catalyzes the hydroxylation in the 1' and 2' positions of the benzene moiety of 3-phenoxybenzoate, yielding 3-hydroxybenzoate and catechol. Transcription of pbaA1A2B and pbaC was induced by 3-phenoxybenzoate, but the transcriptional level of pbaC was far less than that of pbaA1A2B, implying the possibility that PbaC may not be the only reductase that can physiologically transfer electrons to PbaA1A2B in strain JZ-1. Some GR-type reductases from other sphingomonad strains could also transfer electrons to PbaA1A2B, suggesting that PbaA1A2B has a low specificity for reductase.

Figures

FIG 1
FIG 1
Degradation of 3-phenoxybenzoate (■) by strain JZ-1 and its growth (○) along with the yield of 3-hydroxybenzoate (▲) in MSM supplemented with 0.5 mM 3-phenoxybenzoate as the carbon source under aerobic conditions. The data are represented as the mean ± standard deviation for triplicate experiments.
FIG 2
FIG 2
Degradation pathway of 3-phenoxybenzoate in strain JZ-1 and organization of the genes involved in the pathway. (A) Proposed degradation pathway of 3-phenoxybenzoate by strain JZ-1; (B) structure of 3-phenoxybenzoate showing the position of each carbon atom; (C) pattern of 3-phenoxybenzoate cleavage by PobAB from P. pseudoalcaligenes POB310 (3); (D) organization of the genes involved in 3-phenoxybenzoate catabolism in strain JZ-1. CoA, coenzyme A.
FIG 3
FIG 3
Transcriptional levels of pbaA1A2B and pbaC of strain JZ-1 under 3-phenoxybenzoate induction.

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