Question:
Vitamin K is involved in the post-translational modification of which amino acid?
Vitamin K is involved in the post-translational modification of which amino acid?
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Think gamma-carboxylation and the Gla domains of clotting factors.
Updated On: Jun 24, 2026
- Glutamate
- Aspartate
- Tyrosine
- Tryptophan
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Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Step 1: Vitamin K acts as a coenzyme for the enzyme gamma-glutamyl carboxylase.
Step 2: This enzyme carries out the post-translational gamma-carboxylation of specific glutamate (Glu) residues, converting them to gamma-carboxyglutamate (Gla) residues.
Step 3: The added carboxyl groups let these residues chelate calcium, which is essential for the activity of vitamin K-dependent clotting factors II, VII, IX, X and proteins C and S.
Step 4: The modification targets glutamate, not aspartate, tyrosine, or tryptophan. (Tyrosine and aspartate undergo other unrelated modifications; vitamin K is specific to glutamate carboxylation.)
Conclusion: Vitamin K modifies glutamate residues, option A, matching the printed key.
Step 2: This enzyme carries out the post-translational gamma-carboxylation of specific glutamate (Glu) residues, converting them to gamma-carboxyglutamate (Gla) residues.
Step 3: The added carboxyl groups let these residues chelate calcium, which is essential for the activity of vitamin K-dependent clotting factors II, VII, IX, X and proteins C and S.
Step 4: The modification targets glutamate, not aspartate, tyrosine, or tryptophan. (Tyrosine and aspartate undergo other unrelated modifications; vitamin K is specific to glutamate carboxylation.)
Conclusion: Vitamin K modifies glutamate residues, option A, matching the printed key.
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