Substrate and thiol specificity of a stress-inducible glutathione transferase from soybean

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