Question:
Which selenoprotein is involved in the conversion of thyroid hormone \(T_4\) into \(T_3\)?
Which selenoprotein is involved in the conversion of thyroid hormone \(T_4\) into \(T_3\)?
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"De-iodinase" implies the removal of iodine.
Since thyroid hormones (\(T_4\), \(T_3\)) are iodinated tyrosine derivatives, the enzyme responsible for their conversion must logically be a deiodinase.
Since thyroid hormones (\(T_4\), \(T_3\)) are iodinated tyrosine derivatives, the enzyme responsible for their conversion must logically be a deiodinase.
Updated On: Jul 8, 2026
- Thioredoxin reductase
- Glutathione peroxidase
- Selenophosphatesynthetase
- Iodothyronine 5'-deiodinase
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Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Selenium is a vital trace mineral incorporated into selenoproteins as selenocysteine. These enzymes play vital roles in antioxidant defense and thyroid hormone metabolism.
Step 3: Detailed Explanation:
1. Thyroxine (\(T_4\)) is the major secretory product of the thyroid gland, but it is a prohormone.
2. For physiological activity, \(T_4\) must be converted into the active form, triiodothyronine (\(T_3\)).
3. This conversion involves the removal of a 5'-iodine atom from the outer ring of \(T_4\).
4. This reaction is catalyzed by Iodothyronine 5'-deiodinase (types I, II, and III), which is a key selenium-dependent enzyme (selenoprotein).
5. Other options like Thioredoxin reductase and Glutathione peroxidase are also selenoproteins, but they function in redox regulation and antioxidant defense rather than thyroid hormone conversion.
Step 4: Final Answer
The correct option is (D).
Selenium is a vital trace mineral incorporated into selenoproteins as selenocysteine. These enzymes play vital roles in antioxidant defense and thyroid hormone metabolism.
Step 3: Detailed Explanation:
1. Thyroxine (\(T_4\)) is the major secretory product of the thyroid gland, but it is a prohormone.
2. For physiological activity, \(T_4\) must be converted into the active form, triiodothyronine (\(T_3\)).
3. This conversion involves the removal of a 5'-iodine atom from the outer ring of \(T_4\).
4. This reaction is catalyzed by Iodothyronine 5'-deiodinase (types I, II, and III), which is a key selenium-dependent enzyme (selenoprotein).
5. Other options like Thioredoxin reductase and Glutathione peroxidase are also selenoproteins, but they function in redox regulation and antioxidant defense rather than thyroid hormone conversion.
Step 4: Final Answer
The correct option is (D).
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