Which antioxidant enzymes protect the lens from cataracts?

• A. SOD, catalase, glutathione peroxidase.
• B. Vitamin C, Vitamin E, Selenium.
• C. Superoxide dismutase only.
• D. Catalase and peroxidase only.

Answer: (A)

The lens relies on enzymatic antioxidants to neutralize reactive oxygen species that build up from UV exposure and normal metabolism, preventing damage to lens proteins that can lead to cataracts. The key enzymatic defenses are superoxide dismutase, catalase, and glutathione peroxidase. Superoxide dismutase converts the harmful superoxide radical into hydrogen peroxide. Catalase then breaks that hydrogen peroxide down into water and oxygen, removing a reactive species before it can injure cellular components. Glutathione peroxidase also reduces hydrogen peroxide and lipid hydroperoxides, using glutathione as a substrate, which protects membrane lipids and crystallin proteins in the lens from oxidative damage. Together, these enzymes form a coordinated system to keep oxidative stress under control in the lens.

Vitamins like C and E are non-enzymatic antioxidants, and selenium is a necessary cofactor for glutathione peroxidase, not an enzyme itself, so they do not constitute the enzymatic trio that directly scavenges reactive oxygen species in the lens.