We propose to continue the study of glutathione synthesis and metabolism in the lens in which we have already made considerable progress. The maintenance of a high level of reduced glutathione is recognized as essential in the prevention of certain types of cataract formation and progression. Utilizing procedures already established in this laboratory for organ lens culture, enzyme purification, assay, and kinetic studies, we plan 1) to investigate certain key enzymes in glutathione synthesis and metabolism, especially in relation to aging and safe use of pharmaceuticals. These enzymes include coenzyme A-acetyl transferase, glutathione S-transferase and the mercapturic acid pathway, and the first three enzymes in the transformation of methionine to cysteine. 2) To determine the amount of free and bound glutathione in situ in both aging and cataractous lenses by means of NMR spectroscopy; and the concentrations of ADP and substrates of glutathione synthesis in the aging human lens by HPLC or the amino acid analyzer. 3) To establish the roles of glutathione peroxidase and catalase in the prevention of oxidative damage in the organ cultured lens. 4) To study the effect of both reduced and oxidized glutathione on Na-K-ATPase. 5) To examine the possible role of a glutathione analogue, arising from homocysteine, in patients suffering from homocystinuria. These studies will further expand our knowledge of glutathione and its role in the maintenance of a clear lens.
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