In addition to the above twenty amino acids, there are other amino acids, which have limited distribution and high amounts in few proteins.

Examples

Hydroxy proline – 12% collagen

Hydroxy lysine – 1% collagen

N-methyl lysine – Myosin

γ-carboxyglutamate – Blood-clotting protein

α-aminoadipate – Corn protein

α-έ-diaminopimelate – Bacterial protein