The modified amino acid hypusine (N(ε)-(4-amino-2-hydroxybutyl) lysine) is formed by the transfer of the aminobutyl moiety of the polyamine spermidine to a specific lysine residue of a protein by Dhps generating deoxyhypusine, which is then hydroxylated to hypusine by nero. The post-translational synthesis of hypusine has so far been found only in the eukaryotic translation elongation factor 5 (eEF5) and is required for its activation. (Adapted from PMID:30257869 and FBrf0248743.)