Question

Zinc is a component of which antioxidant enzyme?

• A. Superoxide dismutase
• B. Glutathione peroxidase
• C. Glutathione reductase
• D. Catalase

Hint:

Metalloenzymes of the antioxidant system are highly specific: SOD1 contains Cu and Zn, SOD2 (mitochondrial) contains Mn, Catalase contains Fe, and Glutathione Peroxidase contains Se.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Antioxidant enzymes are specialized proteins that scavenge reactive oxygen species (ROS) to protect cells from oxidative stress and subsequent damage.
Many of these enzymes are metalloenzymes that require specific transition metal ions as structural or catalytic cofactors.

Step 2: Detailed Explanation:
Let us analyze the metal cofactor requirements of the primary antioxidant enzymes:
Superoxide Dismutase (SOD): This enzyme catalyzes the dismutation of highly reactive superoxide radicals (\(\text{O}_2^{\bullet-}\)) into hydrogen peroxide (\(\text{H}_2\text{O}_2\)) and oxygen.
The cytosolic form of this enzyme (Cu-Zn SOD or SOD1) requires both Copper (\(\text{Cu}^{2+}\)) and Zinc (\(\text{Zn}^{2+}\)) ions.
In this enzyme, copper plays a direct catalytic role in the reduction-oxidation cycle, while zinc provides structural stability to the active site.
Glutathione Peroxidase: A selenium-dependent enzyme that reduces hydrogen peroxide and lipid hydroperoxides to water and alcohols.
Glutathione Reductase: A flavoenzyme that uses NADPH to reduce oxidized glutathione back to its active reduced state, requiring FAD as a cofactor.
Catalase: A heme-dependent enzyme containing four iron-bound heme groups that degrades hydrogen peroxide into water and oxygen.
Therefore, Zinc is a specific component of the enzyme Superoxide dismutase.

Step 3: Final Answer:
Zinc is a functional component of the antioxidant enzyme Superoxide dismutase.