Activity of glutathione synthesis enzymes in the rhesus monkey lens related to age: a model for the human lens.
The low activity level of lenticular gamma-glutamylcysteine synthetase appears to be an evolutionary phenomenon restricted to higher primates. Rapid reduction with age of the activity of both enzymes (gamma-glutamylcysteine synthetase and glutathione synthetase) required for glutathione synthesis in the human lens was demonstrated in an earlier study. The activities of gamma-glutamylcysteine synthetase and glutathione synthetase, the two enzymes responsible for glutathione synthesis, were determined in 39 lenses from the rhesus monkey (Macaca mulatta) as a function of age. The ages ranged from 137 day old fetuses to a 34 year old monkey. Glutathione synthetase activity decreased 8-fold (units/g lens), 7-fold (units/mg soluble protein) and 2-fold (units/lens) over the age span studied. gamma-Glutamylcysteine synthetase activity decreased 3-fold (units/g lens), 4-fold (units/mg soluble protein) and less than 2-fold (units/lens) over the same age span. A small increase in gamma-glutamylcysteine synthetase activity (units/lens) from embryonic lenses to birth and one year of age was followed in later years by a decrease in activity. In adults, the overall ratio of glutathione synthetase activity to gamma-glutamylcysteine synthetase activity was 42:1 as compared to 77:1 for the human and 2:1 to 4:1 for common domestic species. The aging study data indicate that the rhesus monkey lenticular glutathione synthesis system appears to be a good model for the human lens enzymic system.
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D000375:Aging; D000818:Animals; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism*; D005978:Glutathione / Q000096:biosynthesis; D005981:Glutathione Synthase / Q000378:metabolism*; D006801:Humans; D007908:Lens, Crystalline / Q000033:anatomy & histology / Q000201:enzymology / Q000254:growth & development*; D008253:Macaca mulatta; D009929:Organ Size; D010453:Peptide Synthases / Q000378:metabolism*; D013045:Species Specificity
D010453:Peptide Synthases; D005721:Glutamate-Cysteine Ligase; D005981:Glutathione Synthase; D005978:Glutathione