GLUTATHIONE-S-TRANSFERASE OF GOAT LENS - EVIDENCE FOR EXPRESSION OF ONLY CLASS MU-ISOENZYMES

Purpose. It has been suggested that glutathione S-transferases (GSTs) of the mammalian ocular lens detoxify various toxicants and cataractog ens; therefore, it provides protection against cataractogenesis. In th is study the GST isoenzymes of goat lens have been purified and charac terized. Methods. The goat lens homogenate was subjected to affinity c hromatography over GSH-linked epoxy activated Sepharose 6B. The isoenz ymes of the GST were separated by chromatofocusing on a Mono-P column using FPLC(R). Results. Two GST isoenzymes, GST 7.2 and GST 6.6, were purified to apparent homogeneity from goat lens. GST 7.2 appeared to b e a heterodimer of Mr. 26,500 and Mr. 25,000 subunits, the GST 6.6 sho wed a humodimeric subunit structure of Mr. 25,000. Western blotting an d the N-terminal region amino acid sequence analysis indicated that bo th isoenzymes of goat lens belong to the mu-class GST. Conclusion. Alt hough they share varying degrees of structural correlation, the two is oenzymes of goat lens seem to be the products of two distinct genes. T he isoenzyme expression pattern of GST in goat lens is similar to bovi ne lens, which also contains two isoenzymes belonging only to GST mu.