Partial Properties of Four Glycosidases in Normal Human Lens and Variations in Their Enzyme Activites during Aging and with the Advance of Lens Coloration

Abstract

This paper reports the active glycosidases in normal human lenses and their partial properties. In addition, variations in their enzyme activities during aging and with the advance of lens coloration were also examined. Five glycosidases, α-D-glucosidase, β-D-glucuronidase, N-acetyl-β-D-glucosaminidase, β-D-cellobiosidase, and α-L-fucosidase, were detercted as active glycosidases in the normal human lens. However, the activity of β-D-cellobiosidase was considerably low as compard to the other four glycosidases. Thus, this enzyme was omitted from this study. The four glycosidases, α-D-glucosidase, β-D-glucuronidase, N-acetyl-β-D-glucosaminidase, and α-L-fucosidase, showed that their enzyme activities fell abruptly between the ages of 40 and 50. Furthermore, the K_m values of their enzymes exhibited some variability during aging. Namely, the K_m values of their enzymes indicated the lowest value between the 40 age group and 50 age group, suggesting that the substrate affinity became the strongest at these age groups.Then, variations in enzyme activity with the advance of lens coloration were examined. In each cases, the specific activity of detectable glycosidases in color lenses, white to brown, decreased. In particular, the specific activity of enzymes in the brown lens was very low, indicating that glycosidases in the brown lens may scarcely display their enzyme activities.