ORM2 belongs to the calycin superfamily, lipocalin family. Lipocalins share limited regions of sequence homology and a common tertiary structure architecture. They transport small hydrophobic molecules such as steroids, bilins, retinoids, and lipids. Lipocalins can be found in gram-negative bacteria, vertebrate cells, and invertebrate cells, and plants. They are associated with many biological processes. ORM2 functions as a transport protein in the bloodstream. It is expressed by the liver and secreted in plasma. It seems that ORM2 function in modulating the activity of the immune system during the acute-phase reaction. It binds various hydrophobic ligands in the interior of its beta-barrel domain. It also binds synthetic drugs and influences their distribution and availability.