Activity loss of glutathione synthesis enzymes associated with human subcapsular cataract.

PURPOSE To assess the activities of the two enzymes required for glutathione synthesis, gamma-glutamylcysteine synthetase and glutathione synthetase, in various forms of human cataracts. METHODS The Cooperative Cataract Research Group cataract classification method and standard enzyme assay procedures were used. RESULTS An inverse relationship was shown between residual activity of each of the glutathione synthesis enzymes and degree of subcapsular cataract. A weaker inverse relationship existed between glutathione synthetase activity and supranuclear and nuclear cataracts. No other parameters yielded comparable correlations with the activity of either enzyme. CONCLUSIONS Activity loss of the glutathione synthesis enzymes is associated with human subcapsular cataract formation.