Phosphomannose binding proteins: the phosphomannosyl receptor and insulin like growth factor II receptor

Proteins that bind phosphomannose residues in glycoproteins exhibit widely different functions. They are found as receptors of lysosomal enzymes, as ligatin that binds peripheral glycoproteins and as a lectin in parasites. The identity of the phosphomannosyl receptor for lysosomal enzymes and the insulin like growth factor II receptor raises interesting questions regarding their function.