Probably involved in lipid transport. Can bind sphingosine-1-phosphate, myristic acid, palmitic acid and stearic acid, retinol, all-trans-retinoic acid and 9-cis-retinoic acid (By similarity). Interacts with LRP2; LRP2 mediates APOM renal uptake and subsequent lysosomal degradation. Expressed by the liver; secreted in plasma. Belongs to the calycin superfamily. Lipocalin family. Highly divergent.