Non-proteinogenic amino acids

In biochemistry, non-coded or non-proteinogenic amino acids are those not naturally encoded or found in the genetic code of any organism.Despite the use of only 22 amino acids (21 in eukaryotes) by the translational machinery to assemble proteins (the proteinogenic amino acids), over 140 amino acids are known to occur naturally in proteins and thousands more may occur in nature or be synthesized in the laboratory.Many non-proteinogenic amino acids are noteworthy because they are;Selenocysteine. This amino acid contains a selenol group on its β-carbonPyrrolysine. This amino acid is formed by joining to the ε-amino group of lysine a carboxylated pyrroline ringβ-alanine: an amino acid produced by aspartate 1-decarboxylase and a precursor to coenzyme A and the peptides carnosine and anserine.γ-Aminobutyric acid (GABA): a neurotransmitter in animals.δ-Aminolevulinic acid: an intermediate in tetrapyrrole biosynthesis (haem, chlorophyll, cobalamin etc.).4-Aminobenzoic acid (PABA): an intermediate in folate biosynthesisalanineaminoisobutyric aciddehydroalaninecystinecystathioninelanthionineDjenkolic acidDiaminopimelic acidGlycine (Hydrogen side-chain)Alanine (Methyl side-chain)α-aminobutyric acid (Ethyl side-chain)Norvaline (n-Propyl side-chain)Norleucine (n-Butyl side-chain)Homonorleucine (n-Pentyl side-chain)Carboxyglutamic acid. Whereas glutamic acid possess one γ-carboxyl group, Carboxyglutamic acid possess two.Hydroxyproline. This imino acid differs from proline due to a hydroxyl group on carbon 4.Hypusine. This amino acid is obtained by adding to the ε-amino group of a lysine a 4-aminobutyl moiety (obtained from spermidine)Pyroglutamic acidThialysineQuisqualic acidCanavanineazetidine-2-carboxylic acidCephalosporin CPenicillamine In biochemistry, non-coded or non-proteinogenic amino acids are those not naturally encoded or found in the genetic code of any organism.Despite the use of only 22 amino acids (21 in eukaryotes) by the translational machinery to assemble proteins (the proteinogenic amino acids), over 140 amino acids are known to occur naturally in proteins and thousands more may occur in nature or be synthesized in the laboratory.Many non-proteinogenic amino acids are noteworthy because they are; Technically, any organic compound with an amine (-NH2) and a carboxylic acid (-COOH) functional group is an amino acid. The proteinogenic amino acids are small subset of this group that possess central carbon atom (α- or 2-) bearing an amino group, a carboxyl group, a side chain and an α-hydrogen levo conformation, with the exception of glycine, which is achiral, and proline, whose amine group is a secondary amine and is consequently frequently referred to as an imino acid for traditional reasons, albeit not an imino. The genetic code encodes 20 standard amino acids for incorporation into proteins during translation. However, there are two extra proteinogenic amino acids: selenocysteine and pyrrolysine. These non-standard amino acids do not have a dedicated codon, but are added in place of a stop codon when a specific sequence is present, UGA codon and SECIS element for selenocysteine, UAG PYLIS downstream sequence for pyrrolysine.All other amino acids are termed 'non-proteinogenic'. There are various groups of amino acids: These groups overlap, but are not identical. All 22 proteinogenic amino acids are biosynthesised by organisms and some, but not all, of them also are abiotic (found in prebiotic experiments and meteorites). Some natural amino acids, such as norleucine, are misincorporated translationally into proteins due to infidelity of the protein-synthesis process. Many amino acids, such as ornithine, are metabolic intermediates produced biosynthetically, but not incorporated translationally into proteins. Post-translational modification of amino-acid residues in proteins leads to the formation of many proteinaceous, but non-proteinogenic, amino acids. Other amino acids are solely found in abiotic mixes (e.g. α-methylnorvaline). Over 30 unnatural amino acids have been inserted translationally into protein in engineered systems, yet are not biosynthetic. In addition to the IUPAC numbering system to differentiate the various carbons in an organic molecule, by sequentially assigning a number to each carbon, including those forming a carboxylic group, the carbons along the side-chain of amino acids can also be labelled with Greek letters, where the α-carbon is the central chiral carbon possessing a carboxyl group, a side chain and, in α-amino acids, an amino group – the carbon in carboxylic groups is not counted. (Consequently, the IUPAC names of many non-proteinogenic α-amino acids start with 2-amino- and end in -ic acid.)