Misplaced Pages

This is an old revision of this page, as edited by Gianluca.molla (talk | contribs) at 09:29, 17 November 2016. The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

This article needs more links to other articles to help integrate it into the encyclopedia. Please help improve this article by adding links that are relevant to the context within the existing text. (October 2016) (Learn how and when to remove this message)

This article needs attention from an expert on the subject. Please add a reason or a talk parameter to this template to explain the issue with the article. When placing this tag, consider associating this request with a WikiProject. (October 2016)

Amino acids are chiral compounds that are present in living organisms as free compounds or as polymers such as peptides or proteins. The 20 L-Amino acids present in proteins and peptides are defined as proteinogenic amino acid. About 500 amino acids are known and have been classified in many ways base on their chemical/physical properties.

All α-amino acids (AA) but glycine exist in either of the two enantiomers, which are mirror images of each other (the so called D- and L-enantiomers).

Although present in a less concentration in mammals, free D-amino acids play central roles: as an example D-serine is one of the main neuromodulators of the glutamatergic neurotransmission and D-aspartate is fundamental for brain development in fetus.

Bacteria: The major sources of D-amino acids in Nature are bacteria. In these microorganisms, D-amino acids are part of peptidoglycan (a major component of the bacterial cell wall). In addition, also the compounds teichoic acids and poly-γ-glutamate contain D-amino acids.

In peptidoglycan, D-alanine or D-glutamate contribute to antibiotic resistance in some bacteria. Many diverse bacteria synthesize D-amino acids such as, D-methionine and D-leucine.

D-amino acids are also present in many venoms from platypus, funnel web spider, and cone snail produced by the action of isomerases.

References

1. Wagner I, Musso H (November 1983). "New Naturally Occurring Amino Acids". Angewandte Chemie International Edition in English. 22 (11): 816–28. doi:10.1002/anie.198308161.
2. Katane M, Homma H (June 2010). "D-aspartate oxidase: the sole catabolic enzyme acting on free D-aspartate in mammals". Chem Biodivers. 7 (6): 1435–49. doi:10.1002/cbdv.200900250. PMID 20564562.
3. Mothet JP, Parent AT, Wolosker H, Brady RO, Linden DJ, Ferris CD, Rogawski MA, Snyder SH (April 2000). "D-serine is an endogenous ligand for the glycine site of the N-methyl-D-aspartate receptor". Proceedings of the National Academy of Sciences of the United States of America. 97 (9): 4926–31. Bibcode:2000PNAS...97.4926M. doi:10.1073/pnas.97.9.4926. PMC 18334. PMID 10781100.
4. Radkov AD, Moe LA (2014). "Bacterial synthesis of D-amino acids". Appl Microbiol Biotechnol. 98: 5363–74. doi:10.1007/s00253-014-5726-3.

External links

• A world in the mirror: D-amino acids

v t e Encoded (proteinogenic) amino acids
General topics	Protein Peptide Genetic code
By properties	Aliphatic Branched-chain amino acids (Valine Isoleucine Leucine) Methionine Alanine Proline Glycine Aromatic Histidine Tyrosine Tryptophan Phenylalanine Polar, uncharged Asparagine Glutamine Serine Threonine Positive charge (pKa) Lysine (≈10.8) Arginine (≈12.5) Histidine (≈6.1) Pyrrolysine Negative charge (pKa) Aspartic acid (≈3.9) Glutamic acid (≈4.1) Selenocysteine (≈5.4) Cysteine (≈8.3) Tyrosine (≈10.1)
Amino acids types: Encoded (proteins) Essential Non-proteinogenic Ketogenic Glucogenic Secondary amino Imino acids D-amino acids Dehydroamino acids

• Chemistry

This biochemistry article is a stub. You can help Misplaced Pages by expanding it.

• v
• t
• e

• Articles with too few wikilinks from October 2016
• Amino acids
• Nitrogen cycle
• Zwitterions
• Biochemistry stubs