Amino acid

This article is about the class of chemicals. For the structures and properties of the standard proteinogenic amino acids, see Proteinogenic amino acid.

Structure of a typical L-alpha-amino acid in the "neutral" form

Amino acids are organic compounds that contain both amino and carboxylic acid functional groups.[1] Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins.[2] Only these 22 appear in the genetic code of life.[3][4]

Amino acids can be classified according to the locations of the core structural functional groups (alpha- (α-), beta- (β-), gamma- (γ-) amino acids, etc.); other categories relate to polarity, ionization, and side-chain group type (aliphatic, acyclic, aromatic, polar, etc.). In the form of proteins, amino-acid residues form the second-largest component (water being the largest) of human muscles and other tissues.[5] Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis. It is thought that they played a key role in enabling life on Earth and its emergence.[6]

Amino acids are formally named by the IUPAC-IUBMB Joint Commission on Biochemical Nomenclature in terms of the fictitious "neutral" structure shown in the illustration. For example, the systematic name of alanine is 2-aminopropanoic acid, based on the formula CH3−CH(NH2)−COOH. The Commission justified this approach as follows:[7]

The systematic names and formulas given refer to hypothetical forms in which amino groups are unprotonated and carboxyl groups are undissociated. This convention is useful to avoid various nomenclatural problems but should not be taken to imply that these structures represent an appreciable fraction of the amino-acid molecules.

  1. ^ Nelson DL, Cox MM (2005). Principles of Biochemistry (4th ed.). New York: W. H. Freeman. ISBN 0-7167-4339-6.
  2. ^ Flissi, Areski; Ricart, Emma; Campart, Clémentine; Chevalier, Mickael; Dufresne, Yoann; Michalik, Juraj; Jacques, Philippe; Flahaut, Christophe; Lisacek, Frédérique; Leclère, Valérie; Pupin, Maude (2020). "Norine: update of the nonribosomal peptide resource". Nucleic Acids Research. 48 (D1): D465–D469. doi:10.1093/nar/gkz1000. PMC 7145658. PMID 31691799.
  3. ^ Richard Cammack, ed. (2009). "Newsletter 2009". Biochemical Nomenclature Committee of IUPAC and NC-IUBMB. Pyrrolysine. Archived from the original on 12 September 2017. Retrieved 16 April 2012.
  4. ^ Rother, Michael; Krzycki, Joseph A. (1 January 2010). "Selenocysteine, Pyrrolysine, and the Unique Energy Metabolism of Methanogenic Archaea". Archaea. 2010: 1–14. doi:10.1155/2010/453642. ISSN 1472-3646. PMC 2933860. PMID 20847933.
  5. ^ Latham MC (1997). "Chapter 8. Body composition, the functions of food, metabolism and energy". Human nutrition in the developing world. Food and Nutrition Series – No. 29. Rome: Food and Agriculture Organization of the United Nations. Archived from the original on 8 October 2012. Retrieved 9 September 2012.
  6. ^ Luisi, Pier Luigi (13 July 2006). The Emergence of Life: From Chemical Origins to Synthetic Biology. Cambridge University Press. p. 13. ISBN 9781139455640. Retrieved 5 August 2024. Of course if on Earth there had only been diketopiperazines and not amino acids; or if sugars did not have the size they have; or if lipids were three times shorter, then we would not have life.
  7. ^ "Nomenclature and Symbolism for Amino Acids and Peptides". IUPAC-IUB Joint Commission on Biochemical Nomenclature. 1983. Archived from the original on 9 October 2008. Retrieved 17 November 2008.