AGE-RELATED INCREASE IN ACTIVITY OF SPECIFIC LYSOSOMAL-ENZYMES IN THEHUMAN RETINAL-PIGMENT EPITHELIUM

Age related changes in the activity of lysosomal enzymes have been stu died in the cultured human retinal pigment epithelium cells collected from 26-85 year old donors. Among four such enzymes studied, activitie s of cathepsin D and beta-glucuronidase increased with the age of the donors while no notable change in activity of arylsulfatase B and alph a-mannosidase was observed. Kinetic parameters of beta-glucuronidase w as measured in retinal pigment epithelium cells isolated from donors o f different ages, Similar kinetic parameters for beta-glucuronidase at different ages suggest that the observed increase in the activity of the enzyme with age is not due to post-translational modification of t he enzyme. Western blot analysis provides evidence for increased synth esis of beta-glucuronidase with aging. Relative proportions of glycosa minoglycans, the natural substrates of beta-glucuronidase and arylsulf atase B, in the retinal pigment epithelium altered with the age of the donors. A significant decrease of dermatan sulfate levels with aging correlates well with the observed increase in the level of beta-glucur onidase activity. (C) 1997 Academic Press Limited.