Recombinant target proteins are often expressed as a fusion product with Glutathione-S-Transferase (GST) tags using various expression vector constructs. Thus, antibodies directed against the GST tags of the recombinant constructs can facilitate the purification and study of target proteins. Monoclonal Anti-Glutathione-S-Transferase (GST) antibody reacts with GST from Schistosoma japonicum. Furthermore, the product identifies native as well as denatured-reduced forms of purified GST and GST fusion proteins. The antibody does not detect GST derived from rat, rabbit, porcine and bovine liver or from human placenta.