Glutathione conjugates catabolism

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

After absorption, methyl bromide or metabolites are rapidly distributed to many tissues including the lung, adrenal gland, kidney, liver, nasal turbinates, brain, testis and adipose tissue. In an inhalation study in rats, the methyl bromide concentrations in tissues reached a maximum after 1 h of exposure, but decreased rapidly. Methyl bromide is probably metabolized by glutathione conjugation, the fonned. S -mcthylglutathione being sequentially catabolized to. S -methyl-L-cystcinc and then to carbon dioxide. 

Lamoureux, G.L., L.E. Stafford, R.H Shimabukuro, and R.G. Zaylskie (1973). Atrazine metabolism in sorghum Catabolism of the glutathione conjugate of atrazine. J. Agric. Food Chem., 21 1020-1030. 

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. 

Figure 1(A). Tridiphane blockage of glutathione-S transferase activity, ana (B) catabolism of the conjugate to an inactive form in various species. Source Replotted from data in Lamoureux and Rusness (22).

Haloalkanes and alkenes. Hexachlorobutadiene is a nephrotoxic industrial chemical, damaging the pars recta of the proximal tubule. Initial conjugation with glutathione is necessary, followed by biliary secretion and catabolism resulting in a cysteine conjugate. The conjugate is reabsorbed and transported to the kidney where it can be concentrated and become a substrate for the enzyme /1-lyase. This metabolizes it into a reactive thiol which may react with proteins and other critical macromolecules with mitochondria as the ultimate target. 

Catabolize the glutathione-herbicide conjugate once inside the vacuole e,g, carboxypeptidases, other peptidases). 

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