Herbicide detoxification glutathione conjugation

Shimabukuro, R.H., G.L. Lamoureux, and D.S. Frear. (1978). Glutathione conjugation A mechanism for herbicide detoxification and selectivity in plants, pp. 133-149. In Pallos, F.M. and J.E. Casida, eds., Chemistry and Action of Herbicide Antidotes. New York Academic Press Inc. 

Figure 9.7 Schematic representation of herbicide detoxification in a plant cell. Both XH and XZ are herbicides entering the oxidation-glucose conjugation pathway and the glutathione-dependent pathway, respectively. XOH is the hydroxylated herbicide XOGlc, XGS and Xcys are the glucose, GSH and Cysteine conjugates respectively. [Reproduced with permission of the authors from K. Kreuz and E. Martinoia, Herbicide Metabolism in Plants Integrated Pathways of Detoxication, in G. T. Brooks and T. R. Roberts, Eds., Pesticide Chemistry and Bioscience, The Food-Environment Challenge, Serial Pub. No. 233, The Royal Society of Chemistry, Cambridge, 1999, pp. 277-287.]...

Fig. 5.2. Examples of herbicide detoxification reactions stimulated by the safener mefenpyr-diethyl. (A) Conjugation reaction of fenoxaprop with glutathione (GSH). (B) Oxidative demethylation of mesosulfuron-methyl.

Many of the metabolic transformations for pesticide detoxification that occur in plants are also found in prokaryotes, especially co-metabolic transformations. Glutathione conjugation of the chloroacteamide herbicides is observed in many species of gram negative bacteria including Pseudomonas sp and various members of the Enterobacteriaceae (57). Most of the degradative steps for FE metabolism in plants (de-esterification to F, and subsequent... 

Table 1. Solubilities and Kom of Herbicides that Undergo Detoxification by Conjugation with Reduced Glutathione...

Other classes of herbicide for which glutathione conjugation constitutes a major detoxification mechanism include the nitrodiphenyl ethers acifluor-fen, fluorodifen, and fomesafen, the chloroacetanilides metola-chlor, alachlor, and propachlor, " the oxirane derivative tridiphane, and the sulfonylurea chlorimuron-ethyl (Classic). The last... 

The same biotypes, Peldon A1 and Lines. El, are also resistant to the gramini-cide fenoxaprop, which is used for selective control of A. myosuroides and other grass weeds in cereals, mainly wheat. On a whole plant level. Lines. El was more resistant than Peldon Al. The selectivity of this herbicide has been attributed to rapid detoxification by GST-catalyzed conjugation in the cereal species. In both resistant A. myosuroides biotypes GST activities towards fenoxaprop were found to be increased to a similar degree, when compared with a susceptible biotype. This was due to increased expression of a constitutive GST and to expression of two novel GST isoenzymes. Furthermore, glutathione levels were increased in the resistant biotypes, in Peldon more than in Lines. The data pointed to an involve-... 

---