2,4-Dichlorophenoxyacetate dioxygenase

Evidence for the involvement of histidine residues in the active site has been obtained from a number of experiments. Treatment with the histidine-selective reagent diethyl pyrocarbonate causes complete loss of activity in prolyl 4-hydroxylase (EC 1.14.11.2) [215] and 2,-4-dichlorophenoxyacetate dioxygenase (TfdA) (EC 1.13.11 group) [211], Site-directed mutagenesis of some of the conserved His residues in prolyl 4-hydroxylase [216] and aspartyl P-hydroxylase (EC 1.14.11.16) [217] also results in the loss of enzymatic activity. More recently, direct spectroscopic evidence for His coordination has been obtained in ESEEM studies of Cu(II)-substituted TfdA [218],... 

Fukumori F, RP Hausinger (1993b) Purification and characterization of 2,4-dichlorophenoxyacetate/a-keto-glutarate dioxygenase. J Biol Chem 268 24311-24317. 

Matheson VG, LJ, Forney, Y Suwa, CH Nakatsu, AJ Sextone, AJ, WE Holben (1996) Evidence for acquisition in nature of a chromosomal 2,4-dichlorophenoxyacetic acid/a-ketoglutarate dioxygenase gene by different Burckholderia spp. Appl Environ Microbiol 62 2457-2463. 

Fukumori F, RP Hausinger (1993) Alcaligenes eutrophus IMP 134 2,4-dichlorophenoxyacetate monooxygenase is an a-ketoglutarate-dependent dioxygenase. J Bacterial 175 2083-2086. 

Sassanella TM, F Fukumori, M Bagdasarian, RP Hausinger (1997) Use of 4-nitrophenoxyacetic acid for detection and quantification of 2,4-dichlorophenoxyacetic acid 2,4-D/a-ketoglutarate dioxygenase activity in 2,4- D-degrading microorganisms. Appl Environ Microbiol 63 1189-1191. 

However, like TOL, TOM encodes the meta-fission of the resulting catechol (Figure 11.4). Consequently, it is unproductive in the assimilation of chloroaromatics like chlorobenzene and 2-chlorophenol, which are also metabolized to 3-chlorocatechol because of catechol 2,3-dioxygenase inactivation. To avoid a build-up of this product an ortho-cleavage enzyme and downstream enzymes for the complete catabolism of the product were recruited through the introduction of the 2,4-dichlorophenoxyacetic-acid-degradativeplasmid pROlOl (Kaphammer, Kukor Olsen, 1990). 

The degradation of 2,4-dichlorophenoxyacetate The initial 2-keto-glutarate-dependent dioxygenase that results in the production of... 

Suwa, Y., W.E. Olben, and L.J. Forney. 1996. Characterization of chromosomally encoded 2,4-dichlorophenoxyacetic acid-a-ketoglutarate dioxygenase from Burkholderia sp. strain RASC. Appl. Environ. Microbiol. 62 2464-2469. 

The 2,4-dichlorophenoxyacetic acid/a-ketoglutarate dioxygenase could accept 4-nitrophenoxyacetic acid to produce colored 4-nitro-phenol (Sassanella et al. 1997). It was pointed out, however, that a number of strains that were able to degrade 2,4-dichlorophenoxy-acetic acid were unable to accept the surrogate substrate. 

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