Vitamin required for post translational modification of coagulants is
**Core Concept**
Vitamin K plays a crucial role in the post-translational modification of coagulation proteins, specifically the gamma-carboxylation of glutamic acid residues. This process allows coagulation factors II, VII, IX, and X to bind calcium ions and phospholipids, facilitating the coagulation cascade.
**Why the Correct Answer is Right**
Vitamin K serves as a cofactor for the enzyme gamma-glutamyl carboxylase, which catalyzes the conversion of glutamic acid residues to gamma-carboxyglutamic acid residues. This modification enables the coagulation factors to bind to phospholipid surfaces, initiating the coagulation cascade. The gamma-carboxylation process is essential for the proper functioning of these coagulation factors, and its deficiency can lead to bleeding disorders.
**Why Each Wrong Option is Incorrect**
* **Option A:** Vitamin C is involved in the synthesis of collagen and the maintenance of iron levels, but it is not directly involved in the post-translational modification of coagulation proteins.
* **Option B:** Vitamin E is an antioxidant that helps protect cells from damage, but it does not play a role in the coagulation cascade.
* **Option C:** Vitamin B12 is involved in the synthesis of DNA and the metabolism of fatty acids, but it is not directly involved in the post-translational modification of coagulation proteins.
**Clinical Pearl / High-Yield Fact**
Warfarin, a vitamin K antagonist, is commonly used as an anticoagulant to prevent thrombosis. However, it can increase the risk of bleeding in patients with vitamin K deficiency or those taking other medications that interact with warfarin.
**Correct Answer:** C. Vitamin K.