SUBSTRATE AND THIOL SPECIFICITY OF A STRESS-INDUCIBLE GLUTATHIONE TRANSFERASE FROM SOYBEAN

An RT-PCR-derived clone encoding a stress-inducible glutathione transf erase (GSTGm1) from soybean has been over-expressed in E. coli, The en zyme was active as the dimer GSTGm1-1 and showed GST and glutathione p eroxidase activity toward diverse xenabioitics, including analogues of natural stress-metabolites. The selective herbicides, fomesafen and a cifluorfen, were conjugated more actively with homoglutathione (hGSH), the major thiol in soybean, than with glutathione (GSH). No thiol pre ference was shown with the related herbicide, fluorodifen, while GSH w as preferred with metolachlor and most non-herbicide substrates. Simil iar thiol-dependent specificities were observed in GST preparations fr om plants of varying GSH/hGSH content. (C) 1997 Federation of European Biochemical Societies.