Atrazine conjugation with glutathione

The basis of the selectivity and differences in type of activity of the triazines has been discussed thoroughly conjugation with glutathione, via displacement of the chlorine. 

The third metabolic pathway discovered for degradation of triazine herbicides in plants was first reported by Shimabukuro et al. (1970) and involved conjugation of atrazine with glutathione in corn nutrient uptake, excised leaves, and leaf disc experiments. This new degradation mechanism was postulated to be the primary factor in the... 

The conjugation of xenobiotics with glutathione (GSH) in higher plants was first demtxistrated to be a major enzymatic detoxication mechanism with the atrazine herbicide in sorghum, corn, and other atrazine resistant species (77-80) (Equation 15). Since this... 

Shimabukuro et al. (1971), investigating the metabolism of atrazine in maize, found that the tolerance of maize is not brought about by the above nonenzymatic inactivation alone, but that the primary factor is an enzyme, which conjugates triazine with glutathione, which is then converted to the glutamyl-S-cysteine derivative ... 

Glutathione S-transferase enzymes have been detected In a variety of different plant species (24,76.64.97.101.107-110). Howevei, detailed enzyme studies have been limited to corn (24.76, J09., 12 ) and pea (. JOT., 110). The foliar tissue of corn contains a GST Isozyme that appears rather unique In Its ability to catalyze the conjugation of various 2-chloro-s-trlazlnes with GSH (78). The molecular weight and other properties of this Isozyme are similar to those reported for many mammalian GST Isozymes however, the pH optimum of this Isozyme for atrazine Is somewhat lower than that reported for many GST Isozymes (, 78,J09.). When corn Is treated with R-25788, a second Isozyme Is Induced ( ). The Induced Isozyme Is very effective In catalyzing the GSH conjugation of an a-chloroacetamlde herbicide (alachlor), but It was not assayed with atrazine ( ). 

A few populations of Abutilon theophrasti have evolved resistance to triazine herbicides as a result of increased GST conjugation of the herbicide. One resistant population has an increase in GST with specific action against atrazine 23). It has also been suggested that multiple resistance in Alopecurus myosuroides may involve an increase in GST acting as glutathione peroxidase 24). 

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