amino acid proteinogenic amino acid CHEBI:83813 chebi_ontology proteinogenic amino acids canonical amino acids canonical amino acid Any of the 23 α-amino acids that are precursors to proteins, and are incorporated into proteins during translation. The group includes the 20 amino acids encoded by the nuclear genes of eukaryotes together with selenocysteine, pyrrolysine, and <em>N</em>-formylmethionine. Apart from glycine, which is non-chiral, all have <small>L</small> configuration.