Micronutrients — role of selenium: Glutathione peroxidase (a selenoenzyme) primarily performs which reaction in tissues?

Introduction / Context:
Selenium is incorporated as selenocysteine in several antioxidant enzymes, notably glutathione peroxidases (GPx). Understanding the exact chemistry clarifies how selenium deficiency increases oxidative stress.

Given Data / Assumptions:

• Glutathione peroxidase uses reduced glutathione (GSH) as an electron donor.
• Hydroperoxides (ROOH, including H2O2) are damaging reactive oxygen species.

Concept / Approach:
GPx catalyzes the reduction of hydroperoxides to water or alcohols, with concurrent oxidation of GSH to GSSG, thereby detoxifying peroxides.

Step-by-Step Solution:
Recognize reactants: ROOH + 2 GSH → ROH + H2O + GSSG.Classify the reaction: reduction of hydroperoxides.Choose “reduces” rather than vague “scavenges” or incorrect “oxidizes/hydrolyzes.”Confirm selenium’s catalytic role at the active site.

Verification / Alternative check:
Biochemistry texts present the balanced GPx reaction showing reduction of H2O2 or lipid peroxides.

Why Other Options Are Wrong:
“Scavenges” is nonspecific; the enzyme specifically reduces hydroperoxides. “Oxidizes” reverses the chemistry; “hydrolyzes” is incorrect.

Common Pitfalls:
Using “scavenge” generically without specifying the redox direction; confusing catalase vs GPx mechanisms.

Final Answer:
Reduces toxic hydroperoxy compounds in tissues.