Purification and characterization of glutathione S-transferases in human retina

Human retina has two forms of glutathione (GSH) S-transferases. These forms having pI 4.5 and greater than 10 have been purified and their kinetic, structural and immunological characteristics are described. Both the enzymes of human retina do not express glutathione peroxidase II activity. The anionic enzyme (pI 4.5) of retina cross reacts with the antibodies raised against the anionic GSH S-transferases of human lung and placenta but does not cross react with the antibodies raised against the cationic enzymes of human liver. On the other hand, the cationic enzyme (pI greater than 10) of human retina cross reacts with the antibodies raised against the cationic GSH S-transferases of human liver but not with antibodies raised against the anionic enzymes of lung and placenta. Differences in the kinetic characteristics of the two forms of human retinal GSH S-transferases are also indicated. Results of these studies suggest that the anionic enzyme of retina may be similar to the anionic enzymes of lung and placenta. However, the cationic form appears to be different from all other GSH S-transferases of human tissues characterized so far. Human retina has selenium dependent glutathione peroxidase I and in this respect is different from bovine retina which has no glutathione peroxidase I as demonstrated in earlier studies.