Which vitamin is essential for the metabolism of proteins?

Vitamin B6, also known as pyridoxine, plays a crucial role in the metabolism of proteins. It is involved in the transamination and deamination processes, which facilitate the conversion of amino acids, the building blocks of proteins. This vitamin aids in the enzymatic reactions that process amino acids and contributes to the synthesis of neurotransmitters, hemoglobin, and other important molecules derived from proteins.

While other vitamins serve critical functions in the body, they do not have the same direct involvement in protein metabolism. Vitamin A is primarily associated with vision and immune function, Vitamin C is well-known for its role in collagen synthesis and as an antioxidant, and Vitamin D mainly functions in calcium metabolism and bone health. Therefore, Vitamin B6 is specifically noted for its essential role in protein metabolism, making it the correct choice.