Variation in the glycosidase activity of human lens during aging and with advance of senile cataract.
This paper describes the glycosidases in normal lenses and the variation in their activities during aging and with the advance of cataract. In normal human lenses, four glycosidases, alpha-L-fucosidase, alpha-D-glucosidase, beta-D-glucuronidase and beta-D-galactosaminidase, exhibited strong specific activities, which fell sharply between the ages of 40 and 60. In the 50-60 age group the enzyme activities fell sharply to one-tenth and below those in the lenses of the 20-30 age group. The Km value of each enzyme also depended on age and exhibited some variability, suggesting that the substrate affinity of enzyme may be changeable. These facts show that the specific activities and Km values of some glycosidases in normal human lenses change with aging. The activities of the four glycosidases in lenses with senile cataract were also determined as a function of advanced cataract stage. The activities of the four enzymes were weak in the lenses of the younger age groups, and were undetectable in the lenses of older groups, over 60-year of age. This shows that cataract formation may have a deleterious effect on the catalytic activity of some glycosidase and inhibit them strongly.
Kamei
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A
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Meijo University, Nagoya, Japan.
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D002386:Cataract / Q000201:enzymology*; D005959:Glucosidases / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007908:Lens, Crystalline / Q000201:enzymology*; D008875:Middle Aged; D013696:Temperature
D005959:Glucosidases