Post translation carboxylation of clotting factors requires –
**Core Concept**
The question is about the post-translational modification of clotting factors, specifically the process of carboxylation. This process is crucial for the activation of certain clotting factors. The underlying principle involves the addition of a carboxyl group to specific glutamic acid residues, which is necessary for the binding of these factors to phospholipid surfaces.
**Why the Correct Answer is Right**
The correct answer is related to the requirement of vitamin K for the carboxylation of clotting factors. Vitamin K acts as a cofactor for the enzyme gamma-glutamyl carboxylase, which catalyzes the carboxylation of glutamic acid residues on clotting factors II, VII, IX, and X, as well as proteins C and S. This modification is essential for the calcium-dependent binding of these proteins to phospholipid surfaces, a critical step in the coagulation cascade.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while calcium ions are crucial for the binding of carboxylated clotting factors to phospholipid surfaces, they are not directly involved in the carboxylation process itself.
**Option B:** This option is incorrect as it does not directly relate to the carboxylation process of clotting factors.
**Option D:** This option is also incorrect as it is not directly related to the post-translational carboxylation of clotting factors.
**Clinical Pearl / High-Yield Fact**
Vitamin K is essential for the post-translational modification of clotting factors, and its deficiency can lead to bleeding disorders. Newborns are at risk of vitamin K deficiency bleeding, which is why vitamin K is administered at birth.
**Correct Answer:** D. Vitamin K