A glutathione S-transferases isozyme (bGST 5.8) involved in the metabolism of 4-hydroxy-2-trans-nonenal is localized in bovine lens epithelium

Previous studies have suggested that a group of GST isozymes (bGST 5.8) with substrate preference for 4-hydroxy-2-trans-nonenal (4-HNE) were present in bovine retina, cornea, iris-ciliary body and sclera, but not in lens. The present studies demonstrate that bGST 5.8 is present in bovine lens epithelium and absent in the cortex and nucleus. Immunochemical studies demonstrated that the enzyme is selectively expressed in epithelium where it can be induced by about 2.5-fold when the lenses are cultured in Medium-199 for 24 hr in the presence of 10 μM BHT. bGST 5.8 was purified to homogeneity from the epithelium using immunoaffinity chromatography. Upon SDS-PAGE, the enzyme showed a single band corresponding to an M(r) value of 25 kDa and its CNBr-peptide maps in SDS-gels were identical to those of the isozymes of this group of GSTs reported previously. The enzyme exhibited high activity towards 4-HNE, and showed glutathione peroxidase activity towards phospholipid hydroperoxides. The K(m) values of the enzyme for 4-HNE (57 μM from control and 52 μM from BHT-treated) were in the same range as those reported for GSTs 5.8 of human ocular tissues. However, the K(cat) value of the lens epithelium enzyme for 4-HNE (15.4 mol mol^-1 sec^-1 from control, and 20.2 mol mol-¹ sec^-1 from BHT treated) were considerably less than those reported for the human ocular GST 5.8. Results of these studies suggested that a GST isozyme involved in the detoxification of the electrophilic products of lipid peroxidation was localized in the epithelium of bovine lens.