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Ascorbate free radical reductase and ascorbate redox cycle in the human lens
1Department of Ophthalmology, Tokai University School of Medicine, Isehara, Japan.
Japanese Journal of Ophthalmology
|January 1, 1988
Summary
Ascorbate free radical (AFR) reductase activity decreases in cataractous lenses, potentially contributing to oxidative damage and senile cataracts. This enzyme
Area of Science:
- Biochemistry
- Ophthalmology
- Enzymology
Background:
- Senile cataracts are associated with oxidative stress in the human lens.
- Ascorbate (Vitamin C) plays a crucial role in lens redox homeostasis.
- Ascorbate free radical (AFR) is an intermediate in ascorbate oxidation.
Purpose of the Study:
- To investigate the presence and activity of AFR reductase in senile cataractous human lenses.
- To explore the relationship between AFR reductase activity and lens protein insolubility.
- To assess the potential role of AFR reductase in cataract development.
Main Methods:
- Spectrophotometric measurement of NADH oxidation in lens homogenates.
- Determination of Michaelis constants for AFR and NADH.
- Correlation analysis between AFR reductase activity and insoluble lens protein content.
Main Results:
- AFR reductase (NADH:AFR oxidoreductase) was detected in cataractous human lenses.
- The enzyme's Michaelis constants were determined for AFR (approx. 10 microM) and NADH (<1 microM).
- AFR reductase activity decreased with increasing insoluble lens protein, suggesting early decline before aggregation.
Conclusions:
- AFR reductase is vital for maintaining the ascorbate redox cycle in the human lens.
- Reduced activity of AFR reductase, alongside other antioxidant enzymes, may contribute to oxidative damage in senile cataracts.
- Loss of AFR reductase function is implicated in the pathogenesis of senile cataracts.