Which protein complexes with the retinol-binding protein to aid in the metabolism of vitamin A?

The correct answer is prealbumin, which plays a crucial role in the transport and metabolism of vitamin A. Prealbumin, also known as transthyretin, is a transport protein that binds retinol-binding protein (RBP) in the bloodstream. This complex facilitates the transport of retinol, the alcohol form of vitamin A, from the liver to various tissues in the body.

By binding with retinol-binding protein, prealbumin helps stabilize the retinol-RBP complex and prevents the rapid degradation of RBP, thus ensuring an effective delivery of retinol. This interaction is essential for maintaining adequate levels of vitamin A in the body, which is important for various physiological functions, including vision, immune response, and cellular communication.

Overall, the role of prealbumin in the metabolism of vitamin A underscores its importance in the transport system of this vital nutrient, distinguishing it from other proteins, which do not share this specific function in relation to retinol metabolism.