Glutathione Conjugation

Abstract

Glutathione conjugation (GS-atrazine) of the herbicide, 2 -chloro -4 -ethylami no -6 -isopropylamino-s-triazine (atrazine) is another major detoxication mechanism in leaf tissue of corn (Zea mays, L.). The identification of GS-atrazine is the first example of glutathione conjugation as a biotransformation mechanism of a pesticide in plants. Recovery of atrazine-inhibited photosynthesis was accompanied by a rapid conversion of atrazine to GS-atrazine when the herbicide was introduced directly into leaf tissue. N-Dealkylation pathway is relatively inactive in both roots and shoots. The nonenzymatic detoxication of atrazine to hydroxyatrazine is negligible in leaf tissue. The hydroxylation pathway contributed significantly to the total detoxication of atrazine only when the herbicide was introduced into the plant through the roots. The metabolism of atrazine to GS-atrazine may be the primary factor in the resistance of corn to atrazine.The selective herbicides 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) and 2-chloro-4,6-bis(ethylamino)-striazine (simazine) are used extensively to control annual weeds in fields of corn and sorghum. These compounds are effective inhibitors of the Hill reaction in photosynthesis (7) and also reduce the rate of "4CO2 fixation in plants (1, 16).The rate of atrazine metabolism in higher plants is an important factor in herbicidal selectivity (9). Detoxication of atrazine was reported to occur by the 2-hydroxylation and N-dealkylation pathways in higher plants (9, 10). In sorghum a rapid conversion of atrazine to a water-soluble compound (metabolite B) resulted in a recovery of atrazine-inhibited photosynthesis (14). The subsequent identification of metabolite B as a mixture of two closely related compounds, GS-atrazinel and y-glutamyl-S-(4-ethylamino-6-isopropylamino-2-s-triazino)cysteine, indicated the presence of a third detoxication pathway present in higher plants (6). In this paper, the mixture will be referred to as GS-'

Interaction between cadmium and atrazine during uptake by rice seedlings (Oryza sativa L.)

“…Although numerous papers have dealt with the toxicity and fate of atrazine and Cd in the environment (Shimabukuoro et al, 1970;Liu et al, 1999;Katz et al, 2000;Wiegand et al, 2000;Zhao et al, 2003), few studies focused on their effects as mixtures. In fact, atrazine contains five electron-donor atoms that could potentially participate in the formation of metal/atrazine complexes.…”

Screening for DIMBOA (benzoxazinone) concentration among South African inbred maize lines and sorghum cultivars

“…However, N-dealkylation and conjugation also takes place in these plants which could in part be responsible for the results obtained by i.e Court de Billot & Nel (1980;1981). Grouping all investigated lines according to root DIMBOA concentration, the main site for hydroxylation for atrazine according to Shimabukuro et al (1970) will obviously result in a different order of arrangement as can be inferred from Figure 1. Based on such a classification, T111 could be considered the least tolerant line and M103W the most tolerant.…”

“…N-dealkylation is responsible for the detoxification of a small percentage of atrazine in maize plants, whilst glutathione (peptide) conjugation represents the main detoxifying mechanism in leaves of maize plants (Shimabukuro, 1967;1968;Shimabukuro & Swanson, 1969;Shimabukuro et al_ 1970).…”

“…Hydroxylation of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) in the presence of DIMBOA (benzoxazinone) (2,4-dihydroxy-7 -methoxy-l ,4-benzoxazine-3-one) or its 2-glucoside to hydroxyatrazine, is the main detoxifying mechanism of the roots of pre-emergence treated maize plants (Shimabukuro, 1967;1968;Shimabukuro, Swanson & Walsh, 1970). N-dealkylation is responsible for the detoxification of a small percentage of atrazine in maize plants, whilst glutathione (peptide) conjugation represents the main detoxifying mechanism in leaves of maize plants (Shimabukuro, 1967;1968;Shimabukuro & Swanson, 1969;Shimabukuro et al_ 1970).…”

Stability of Chloroplastic Triazine Resistance in Rutabaga Backcross Generations

“…Subsequent investigations revealed that triazine resistance in birdsrape was cytoplasmically inherited through the female parent and involved modification of the active site in the chloroplasts (8,24) as observed in other triazine resistant weeds. Unlike triazine tolerance in corn (23) decisive role for triazine resistance in this weed species (3). Triazine resistance from birdsrape was transferred by conventional backcross methods into Brassica crops of commercial significance including oil rapeseed (6), rutabaga and Chinese cabbage (25) so that numerous dicotyledonous weeds, including cruciferous weeds, could be controlled with triazine herbicides in these cruciferous crops.…”