Disease relevance of tfdA

• Analysis, cloning, and high-level expression of 2,4-dichlorophenoxyacetate monooxygenase gene tfdA of Alcaligenes eutrophus JMP134 [1].
• Pseudomonas sp. strain B13, containing the cloned tfdA, was able to degrade phenoxyacetic acid and 4-chlorophenoxyacetic acid [1].
• Using recombinant Escherichia coli cells that overexpress the tfdA gene, the thermolabile enzyme (stable only up to 30 degrees C) was purified to apparent homogeneity (specific activity of 16.9 mumol of substrate converted min-1 mg of protein-1) by a simple two-step procedure [2].
• Members of the alpha subdivision of the Proteobacteria class, mostly of the genus Sphingomonas, did not hybridize to either tfdA or tfdC, but some hybridized at low stringency to tfdB [3].
• Members of the beta subdivision of the Proteobacteria class, specifically Alcaligenes, Burkholderia, and Rhodoferax species, carried DNA fragments with 60% or more sequence similarity to tfdA of pJP4, and most carried fragments showing at least 60% homology to tfdB [3].

High impact information on tfdA

• A sharp increase in mRNA levels for tfdA, tfdCDEF-B, tfdDIICIIEIIFII-BII and tfdK was detected between 2 and 13 min after exposure to 2,4-D [4].
• In vivo recombinants of pYG1010 and a cloned tfdS gene rescued the 2,4-D phenotype, indicating that TfdS is a positive regulator of tfdA expression, but not for tfdCDEF expression [5].
• The plasmid genes specifying 2,4-D and 3-Cba catabolism are organized in three operons: tfdA, tfdB, and tfdCDEF [5].
• The other recombinant plasmid (pJP4-FM) should harbor two copies of the tfdA gene but no copies of the tfd gene clusters [6].
• Degradation of 4-chloro-2-methylphenoxyacetic acid in top- and subsoil is quantitatively linked to the class III tfdA gene [7].

Chemical compound and disease context of tfdA

• The Alcaligenes eutrophus JMP134 plasmid pJP4 contains genes necessary for the complete degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and 3-chlorobenzoic acid. tfdA encodes 2,4-D monooxygenase, the initial enzyme in the 2,4-D catabolic pathway [8].

Biological context of tfdA

• Gene tfdA, which codes for the 2,4-D monooxygenase, has now been found by mutagenesis with transposon Tn5 [1].
• Sequence analysis revealed an open reading frame of 861 bases which was identified as the coding region of tfdA by insertion mutagenesis [1].
• The data presented here indicate that tfdA genes can be found on the chromosome of some bacterial species and suggest that these catabolic genes are rather mobile and may be transferred by means other than conjugation [9].
• An XbaI-PstI fragment, containing the complete ORF, encodes a 32,000-Da protein which binds to the promoter regions upstream from tfdA and tfdDII [10].
• Thus, an ortho cleavage of catechol was essential for degradation of phenoxyacetic acid, suggesting that a product of the ortho-cleavage pathway, probably cis, cis-muconic acid, is an inducer of tfdA gene expression [11].

Associations of tfdA with chemical compounds

• The other five isolates did not appear to carry tfdA, and 2,4-D-specific alpha-ketoglutarate-dependent dioxygenase activity could not be detected in cell lysates [12].
• Establishment of phenoxyacetic-acid-degrading soil populations by conjugal transfer of tfdA would depend on the presence of phenol-degrading recipients employing an ortho cleavage of catechol [11].
• Utilization of phenoxyacetic acid, by strains using either the ortho or meta cleavage of catechol during phenol degradation, after conjugal transfer of tfdA, the gene encoding a 2,4-dichlorophenoxyacetic acid/2-oxoglutarate dioxygenase [11].

Other interactions of tfdA

• Even more so, one complete ISJP4 plus its tfdA-tfdS intergenic remnant were sufficient to mediate transposition of intervening DNA [13].

Analytical, diagnostic and therapeutic context of tfdA

• Quantitative PCR revealed growth in the tfdA-containing bacterial community, from 500 genes g(-1) soil to approximately 3 x 10(4) genes g(-1) soil and to 7 x 10(5) genes g(-1) soil for topsoil initially added to 2.3 mg MCPA kg(-1) (dry weight) soil and 20 mg MCPA kg(-1) (dry weight) soil, respectively [7].

References