Partial properties of four glycosidases in normal human lens and variations in their enzyme activities during aging and with the advance of lens coloration.
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, alpha-glucosidase, beta-D-glucuronidase, N-acetyl-beta-D-glucosaminidase, beta-D-cellobiosidase, and alpha-L-fucosidase, were detected as active glycosidases in the normal human lens. However, the activity of beta-D-cellobiosidase was considerably low as compared to the other four glycosidases. Thus, this enzyme was omitted from this study. The four glycosidases, alpha-D-glucosidase, beta-D-glucuronidase, N-acetyl-beta-D-glucosaminidase, and alpha-L-fucosidase, showed that their enzyme activities fell abruptly between the ages of 40 and 50. Furthermore, the Km values of their enzymes exhibited some variability during aging. Namely, the Km 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.
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Meijo University, Nagoya, Aichi, Japan.
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Kamei
D000328:Adult; D000375:Aging / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D003459:Crystallins / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006923:Hymecromone / Q000031:analogs & derivatives / Q000378:metabolism; D007700:Kinetics; D007908:Lens, Crystalline / Q000201:enzymology* / Q000502:physiology; D008875:Middle Aged; D013379:Substrate Specificity; D013696:Temperature
D003459:Crystallins; D006923:Hymecromone; D006026:Glycoside Hydrolases