Question

__________ present in milk can scavenge radicals and exhibit antioxidant activity.

• A. Sulphydryl oxidase
• B. Superoxide dismutase
• C. Phosphatase
• D. Mutase

Hint:

Superoxide dismutase (SOD) is an indigenous antioxidant enzyme in milk that converts reactive superoxide radicals into less reactive oxygen and hydrogen peroxide.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Raw milk contains native enzymatic defense systems that help protect its lipid and protein components from oxidative damage caused by reactive oxygen species (ROS).

Step 2: Detailed Explanation:
Superoxide dismutase (SOD) is an indigenous metalloenzyme present in milk.
It functions as an antioxidant by scavenging superoxide radicals (\(\text{O}_2^{\bullet-}\)), which are common initiators of lipid peroxidation.
SOD catalyzes the dismutation of these radicals into oxygen and hydrogen peroxide:
\[ 2\,\text{O}_2^{\bullet-} + 2\,\text{H}^+ \xrightarrow{\text{SOD}} \text{O}_2 + \text{H}_2\text{O}_2 \] The hydrogen peroxide produced is subsequently decomposed by catalase or lactoperoxidase.
This enzymatic pathway helps protect milk lipids from oxidation.
Other enzymes listed do not act as radical scavengers:
Sulphydryl oxidase catalyzes the oxidation of sulfhydryl groups to disulfide bonds using molecular oxygen, which can produce hydrogen peroxide.
Phosphatase catalyzes the hydrolysis of phosphoric acid esters and has no antioxidant properties.
Mutase enzymes catalyze the intramolecular transfer of functional groups.

Step 3: Final Answer:
Therefore, superoxide dismutase is the enzyme in milk that can scavenge radicals and exhibit antioxidant activity.