Electrophoretic and immunological analysis of human glutathione S-transferase isozymes.

Several electrophoretically distinct glutathione S-transferase isozymes from different tissues have been purified and characterized. The data confirm the suggestion that GST-1, GST-2 and GST-3 are the products of separate genetic loci. An apparently muscle-specific isozyme termed GST-4 has been identified and shown to differ structurally from GST-1, GST-2 and GST-3. It is likely that GST-4 is the product of an additional gene locus. Two isozymes termed GST-5 and GST-6 were purified from brain. GST-5 has a different isoelectric point, but shares many structural features with GST-1. GST-5 may be a brain-specific post-translationally modified product of the GST-1 gene. GST-6 is an acidic isozyme found in many tissues. The data indicate that GST-6 is composed of two dissimilar subunits that do not cross-react with antiserum directed against GST-1, GST-2 or GST-3. These observations therefore suggest that GST-6 may have an independent genetic origin.