Well known as detoxification enzymes, the glutathione transferases(GST) also function in prostaglandin and steroid hormone synthesis. The enzymes are dimmers of 25kDa subunits. There are three major groups of GSTs: canonical(or cytosolic) GSTs(cGSTs), mitochondrial GSTs, and microsomal GSTs. GSTs play a role in the metabolism of drugs, pesticides and other xenobiotics. GST is also a widely used fusion partner, since it offers both an easily detectable tag and a simple purification process that has a minimal with little effect on the biological function of the protein of interest. Recombinant hybrids containing a polypeptide fusion partner (termed “affinity tag”) to facilitate the purification of the target polypeptides are widely used. Epitope tags are useful for the labeling and detection of proteins using immunoblotting, immunoprecipitation and immunostaining techniques. Due to their small size, they are unlikely to affect the tagged protein’s biochemical properities. Numerous vectors containing GST-tags have been developed for both prokaryotic and eukaryotic systems over the past decade.