This invention relates to isolated nucleic acid fragments encoding all or a substantial portion of soybean glutathione-S-transferase (GST) enzymes involved in the detoxification of xenobiotic compounds in plants and seeds. The invention also relates to the construction of chimeric genes encoding all or a substantial portion of soybean GST enzymes, host cells transformed with those genes and methods for the recombinant production of soybean GST enzymes. Methods of constructing transgenic plants having altered levels of GST enzymes and screens for identifying soybean GST enzyme substrates and soybean GST enzyme inhibitors are also provided.