Purification and characterization of corn glutathione S-transferase

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Abstract
Two glutathione S-transferase (GST) activities were identified and purified from etiolated corn tissue. The first, designated GST I enzyme, is constitutively present in corn tissue, and the second, designated GST II enzyme, is present only in tissue which has been treated with chemical antidotes which protect corn against chloroacetanilide herbicides. The total activity constitutes approximately 2% of the soluble protein in these tissues. The native forms of these enzymes have molecular weights of approximately 50,000 as determined by Sephadex G-100 chromatography. On sodium dodecyl sulfate-polyacrylamide gels, GST I enzyme migrates primarily as a single band of MW 29,000, and GST II enzyme migrates as primarily 2 bands of MW 29,000 and 27,000. Both enzymes catalyze the formation of a glutathione-herbicide conjugate in vitro when the herbicide alachlor is used as a substrate. This conjugation results in elimination of the biological activity of the herbicide.