Retinoid metabolism during intestinal absorption

A number of enzymes have been described that might participate in the metabolism of dietary carotenes and retinyl esters necessary for absorption. For several steps two or more different activities are known. Which of the candidate enzymes actually is important in normal physiology is generally not known with any certainty. However, various properties of the enzymes, determined in vitro, can suggest the more likely participants. The ability to interact with retinoids bound to the enterocyte-specific cellular retinol-binding protein, type two, is an important determinant in several cases