Glutathione conjugation plants

Plant. Metabolizes in plants forming water soluble, polar, nonvolatile products (Hartley and Kidd, 1987) and glutathione conjugates (Breaux et al., 1987). 

Catabolism of Glutathione Conjugates of Pesticides in Higher Plants... 

Figure 7.2 Metabolism of atrazine in sugarcane plants by (a) ALdcal kylation of the side chains, (b) hydrolysis of the 2-chloro group followed by JV-dealkylation, and (c) displacement of the 2-chloro by glutathione conjugation (Larson and Ash, 1993).

Shimabukuro, R.H., D.S. Frear, S.H.R. Swanson, and W.C. Walsh (1971b). Glutathione conjugation An enzymatic basis for atrazine resistance in corn. Plant Physiol., 47 10-14. 

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. 

Propachlor Is metabolized by this route In both a resistant and a susceptible species (Equation 16). Glutathione conjugation of propachlor occurs very rapidly Un vitro in the absence of GST enzymes (78) and It Is not clear whether differences In GSH and/or GST concentratlois influence the selectivity of propachlor and related herbicides. The concentration of GSH In higher plants Is estimated... 

Most xenobiotic conjugation reactions in plants and animals lead Initially to the fornation of polar products such as glycoside or glutathione conjugates, but several reports indicate that plants (144-148) and animals (249) may also form lipophilic conjugates. 

The fate of plant xenobiotic conjugates I.e. glycosides, malonates, N-acyl-amlno acids, alkyl/aryl glutathiones and derivatives, lipophilic conjugates and polymer conjugates (bound residues). In animals Is reviewed. Some classes are reasonably well-studied but no Information Is available for others. 

As mentioned In the Introduction, malonylatlon of xenobiotics Is apparently unique to plants. The most commonly observed conjugates are 6- -malonyl esters of glucosides (8-10). However, N-malonylatlon of anilines and more commonly tJ-malonylation of xenobiotic amino acids has been observed ( ). Often N-malonylatlon of cysteine will take place as a step In the catabolism of glutathione conjugates. 

The common terminal metabolite of a glutathione conjugate In a mammal Is a mercapturlc acid —-an N-acetyl- -substltuted-L-cystelne. The equivalent In the plant the phytomercapturlc acid — Is an N-malonyl- -substltuted-L-cystelne (Figure 3). The susceptibility of the -malonyl group to hydrolysis In the mammal has not, to our knowledge, been studied. If It Is stable then the phytomercapturlc acid Is likely to be eliminated unchanged (or perhaps S oxldlzed). 

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