Vitamin K is essential for the post-translational modification of clotting factors II, VII, IX, and X. The specific reaction catalysed is:

• A Hydroxylation of proline residues in the precursor proteins
• B Phosphorylation of serine residues in the precursor proteins
• C Methylation of arginine residues in the precursor proteins
• D Gamma-carboxylation of glutamic acid residues in the precursor proteins ✓

Explanation

Vitamin K acts as a cofactor for gamma-glutamyl carboxylase, which carboxylates specific glutamic acid (Gla) residues in clotting factors II, VII, IX, X, and proteins C and S. This gamma-carboxylation enables calcium binding, essential for coagulation cascade activation. Warfarin inhibits vitamin K epoxide reductase. Option A describes vitamin C's role in collagen synthesis.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.