Kamei A
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Meijo University, Nagoya, Japan.
Biol Pharm Bull. 1995 Oct;18(10):1450-3. doi: 10.1248/bpb.18.1450.
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.
本文描述了正常晶状体中的糖苷酶及其在衰老过程和白内障进展过程中的活性变化。在正常人类晶状体中，四种糖苷酶，即α-L-岩藻糖苷酶、α-D-葡萄糖苷酶、β-D-葡萄糖醛酸酶和β-D-半乳糖胺酶，表现出较强的比活性，在40岁至60岁之间急剧下降。在50至60岁年龄组中，酶活性急剧下降至20至30岁年龄组晶状体中酶活性的十分之一及以下。每种酶的Km值也取决于年龄，并表现出一定的变异性，这表明酶的底物亲和力可能是可变的。这些事实表明，正常人类晶状体中某些糖苷酶的比活性和Km值会随着衰老而变化。还测定了老年性白内障晶状体中四种糖苷酶的活性与白内障进展阶段的关系。这四种酶在较年轻年龄组的晶状体中的活性较弱，在60岁以上的老年组晶状体中则检测不到。这表明白内障的形成可能对某些糖苷酶的催化活性产生有害影响并强烈抑制它们。
