Schistosoma japonicum glutathione S-transferase (GST) is a 26,000 Da enzyme that conjugates reduced glutathione to hydrophobic electrophiles. GST is an ideal fusion partner for production of foreign proteins in commercially available expression systems because it can be expressed in high levels in E. coli. The fusion proteins can be purified to homogenity in a single step as the GST portion of the protein binds tightly to immobilized glutathione. Elution can be accomplished using free glutathione. The GST portion of the fusion protein can be separated from the protein of interest by using site-specific proteases. Antibodies directed against GST can be helpful in detecting the fusion protein during purification and to detect cleavage of GST from the protein of interest.