Amidation site

The precursor of hormones and other active peptides which are C-terminally amidated is always directly followed [1,2] by a glycine residue which provides the amide group, and most often by at least two consecutive basic residues (Arg or Lys) which generally function as an active peptide precursor cleavage site. Although all amino acids can be amidated, neutral hydrophobic residues such as Val or Phe are good substrates, while charged residues such as Asp or Arg are much less reactive. C-terminal amidation has not yet been shown to occur in unicellular organisms or in plants.