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, corneal iris-ciliary body and sclera, but n ot in lens. The present studies demonstrate that bGST 5.8 is present i n bovine lens epithelium and absent in the cortex and nucleus. Immunoc hemical studies demonstrated that the enzyme is selectively expressed in epithelium where it can be induced by about 2.5-fold when the lense s are cultured in Medium-199 for 24 hr in the presence of 10 mu M BHT, bGST 5.8 was purified to homogeneity from the epithelium using immuno affinity chromatography, Upon SDS-PAGE, the enzyme showed a single ban d corresponding to an M(r) value of 25 kDa and its CNBr-peptide maps i n SDS-gels were identical to those of the isozymes of this group of GS Ts reported previously. The enzyme exhibited high activity towards 4-H NE, and showed glutathione peroxidase activity towards phospholipid hy droperoxides. The K-m values of the enzyme for 4-HNE (57 mu M from con trol and 52 mu M from BHT-treated) were in the same range as those rep orted for GSTs 5.8 of human ocular tissues. However, the K-cat value o f 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 considera bly less than those reported for the human ocular GST 5.8. Results of these studies suggested that a GST isozyme involved in the detoxificat ion of the electrophilic products of lipid peroxidation was localized in the epithelium of bovine lens. (C) 1996 Academic Press Limited