Which vitamin is primarily involved in the carboxylation of glutamic acid?

Vitamin K plays a critical role in the carboxylation of glutamic acid, which is an important process for the activation of certain proteins involved in blood clotting and bone metabolism. This vitamin facilitates the conversion of specific glutamic acid residues to gamma-carboxyglutamic acid (Gla), allowing these proteins to bind calcium ions. The ability to bind calcium is essential for the functioning of several coagulation factors and other proteins that rely on this modification for their biological activity.

The other vitamins listed do not have a primary role in the carboxylation of glutamic acid. For instance, Vitamin A is predominantly involved in vision and immune function, Vitamin D is crucial for calcium metabolism and bone health, and Vitamin E primarily acts as an antioxidant. Therefore, Vitamin K's specific function in the carboxylation process distinctly highlights its unique and essential role in human physiology.