A dipeptide is an organic compound derived from two amino acids. The constituent amino acids can be the same or different. When different, two isomers of the dipeptide are possible, depending on the sequence. Several dipeptides are physiologically important, and some are both physiologically and commercially significant. A well known dipeptide is aspartame, an artificial sweetener.

thumb|[[Glycylglycine is the simplest dipeptide.]]

Dipeptides are white solids. Many are far more water-soluble than the parent amino acids.

Examples

thumb|200 px|[[Aspartame is produced commercially as an artificial sweetener.]]

Commercial value

About six dipeptides are of commercial interest.

For many amino acids, the ancillary functional groups are protected. The condensation of the amine and the carboxylic acid to form the peptide bond generally employs coupling agents to activate the carboxylic acid.

The Bergmann azlactone peptide synthesis is a classic organic synthesis for the preparation of dipeptides. Dietary proteins are digested to dipeptides and amino acids, and the dipeptides are absorbed more rapidly than the amino acids, because their uptake involves a separate mechanism. Dipeptides activate G-cells found in the stomach to secrete gastrin.

Diketopiperazines (cyclic dipeptides)

thumb|220 px|[[Retosiban is a cyclic dipeptide being investigated as an oral drug.]]Diketopiperazines are a special class of dipeptides, which are cyclic. They form as side products in peptide synthesis. Many have been produced from non-canonical amino acids.

References

  • An introduction to dipeptides at PeptideGuide.