Mammalian legumain (LGMN, asparagine-specific endoprotease) is a subfamily of cysteine proteases with no homology to other known proteases and is found in a wide range of organisms from parasites to plants and animals. LGMN requires acidic conditions for its degradative activity. Cubilin (CUBN), once released from the complex, cycles back to the cell surface. Free 25-hydroxyvitamin D (calcidiol, 25(OH)D) becomes available for further processing (Nykjaer et al. 1999).