A dipeptide is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

derived from two

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...

s. 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 A sugar substitute is a food additive that provides a sweetness like that of sugar while containing significantly less food energy than sugar-based sweeteners, making it a zero-calorie () or low-calorie sweetener. Artificial sweeteners may b ...

Dipeptides are white solids. Many are far more water-soluble than the parent amino acids. For example, the dipeptide Ala-Gln has the solubility of 586 g/L more than 10x the solubility of Gln (35 g/L). Dipeptides also can exhibit different stabilities, e.g. with respect to hydrolysis. Gln does not withstand sterilization procedures, whereas this dipeptide does. Because dipeptides are prone to hydrolysis, the high solubility is exploited in infusions, i.e. to provide nutrition.

Examples

Commercial value

About six dipeptides are of commercial interest. * Aspartame (''N''-L-α-aspartyl-L-phenylalanine 1-methyl ester) is an artificial

sweetener {{Wiktionary, sweetener A sweetener is a substance added to food or drink to impart the flavor of sweetness, either because it contains a type of sugar, or because it contains a sweet-tasting sugar substitute. Many artificial sweeteners have been ...

. *

Carnosine Carnosine (''beta''-alanyl-L-histidine) is a dipeptide molecule, made up of the amino acids beta-alanine and histidine. It is highly concentrated in muscle and brain tissues. Carnosine was discovered by Russian chemist Vladimir Gulevich. Ca ...

(''beta''-alanyl-L-histidine) and Anserine (''beta''-alanyl-''N''-methyl histidine) are highly concentrated in muscle and brain tissues. They are used in sports medicines. *

Acetylcarnosine ''N''-Acetylcarnosine (NAC) (Not to confuse with N-Acetylcysteine) is a naturally occurring Chemical compound, compound chemically related to the dipeptide carnosine. The NAC molecular structure is identical to carnosine with the exception that it ...

, cataract prevention *

Ala-Gln Alanyl-glutamine is a chemical compound which in the form L-alanyl-L-glutamine is used in dietary supplementation, in parenteral nutrition, and in cell culture. It is a dipeptide consisting of alanine and glutamine. Dieterary supplement As a diet ...

and Gly-Tyr, infusion * Val-Tyr, antihypertensive

Other dipeptides

* Homoanserine (''N''-(4-aminobutyryl)-L-histidine) is another dipeptide identified in the brain and muscles of mammals. *

Diphenylalanine Diphenylalanine is a term that has recently been used to describe the unnatural amino acid similar to the two amino acids alanine and phenylalanine. It has been used for the synthesis of pseudopeptide analogues which are capable of inhibiting ce ...

is the most studied building block in peptide nanotechnology *

Kyotorphin Kyotorphin (L-tyrosyl-L-arginine) is a neuroactive dipeptide which plays a role in pain regulation in the brain. It was first isolated from bovine brain, by Japanese scientists in 1979. Kyotorphin was named for the site of its discovery, Kyoto, Ja ...

(L-tyrosyl-L-arginine) is a neuroactive dipeptide which plays a role in pain regulation in the brain. * (or ophidine) (''beta''-alanyl-''N'' ''tau''-methyl histidine) has been identified in the muscles of several species of mammal (including man), and the

chicken The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adu ...

. * Glorin (''N''-propionyl-γ-L-glutamyl-L-ornithine-δ-lac ethyl ester) is a chemotactic dipeptide for the

slime mold Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic mul ...

'' Polysphondylium violaceum''. *

Barettin Barettin is a brominated alkaloid made of a dehydrogenated brominated derivative of tryptophan linked by two peptide bonds to an arginine residue, forming a 2,5-diketopiperazine nucleus. It is a cyclic dipeptide. Barettin is the major compound ...

(cyclo- 6-bromo-8-en-tryptophan)-arginine is a cyclic dipeptide from the marine sponge ''Geodia barretti''. *

Pseudoproline Pseudoproline (also pseudo-proline, ψ-Pro) derivatives are artificially created dipeptides to minimize aggregation during Fmoc solid-phase synthesis of peptides. History The chemical synthesis of large peptides is still limited by problems of ...

* Dialanine is commonly used as a model in

molecular dynamics Molecular dynamics (MD) is a computer simulation method for analyzing the physical movements of atoms and molecules. The atoms and molecules are allowed to interact for a fixed period of time, giving a view of the dynamic "evolution" of t ...

. * Xenortides, isolated from the bacterium '' Xenorhabdus nematophila''

Production

Synthetic dipeptides

Dipeptides are produced by coupling amino acids. The amino group on one amino acid is rendered non-nucleophilic (P in eq) and the carboxylic acid group in the second amino acid is deactivated as its methyl ester. The two modified amino acids are then combined in the presence of a coupling agent, which facilitates formation of the amide bond: :RCH(NHP)CO₂H + R'CH(NH₂)CO₂CH₃ → RCH(NHP)C(O)NH(CHR')CO₂CH₃ + H₂O Subsequent to this coupling reaction, the amine protecting group P and the ester are converted to the free amine and carboxylic acid, respectively. 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.

Biosynthesis

Dipeptides are produced from polypeptides by the action of the

hydrolase Hydrolase is a class of enzyme that commonly perform as biochemical catalysts that use water to break a chemical bond, which typically results in dividing a larger molecule into smaller molecules. Some common examples of hydrolase enzymes are este ...

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

dipeptidyl peptidase. 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)

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

External links

An introduction to dipeptides
at PeptideGuide. {{Peptides