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. Th ...

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 ...

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 Aspartame is an artificial non-saccharide sweetener 200 times sweeter than sucrose and is commonly used as a sugar substitute in foods and beverages. It is a methyl ester of the aspartic acid/phenylalanine dipeptide with the trade na ...

, 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 ...

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 Aspartame is an artificial non-saccharide sweetener 200 times sweeter than sucrose and is commonly used as a sugar substitute in foods and beverages. It is a methyl ester of the aspartic acid/phenylalanine dipeptide with the trade na ...

(''N''-L-α-aspartyl-L-phenylalanine 1-methyl ester) is an artificial sweetener. * Carnosine (''beta''-alanyl-L-histidine) and Anserine (''beta''-alanyl-''N''-methyl histidine) are highly concentrated in

muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

and brain tissues. They are used in sports medicines. * Acetylcarnosine, cataract prevention * Ala-Gln 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 Nanotechnology, also shortened to nanotech, is the use of matter on an atomic, molecular, and supramolecular scale for industrial purposes. The earliest, widespread description of nanotechnology referred to the particular technological goal o ...

* Kyotorphin (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 domestication, domesticated junglefowl species, with attributes of wild species such as the grey junglefowl, grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster ...

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

. *

Xenortide The xenortides (A-D) are a class of linear peptides isolated from the bacterium '' Xenorhabdus nematophila'',{{Cite journal, last=Lang, first=Gerhard, last2=Kalvelage, first2=Tim, last3=Peters, first3=Arne, last4=Wiese, first4=Jutta, last5=Imhoff, ...

s, isolated from the bacterium ''

Xenorhabdus nematophila ''Xenorhabdus'' is a genus of motile, gram-negative bacteria from the family of the Morganellaceae. All the species of the genus are only known to live in symbiosis with soil entomopathogenic nematodes from the genus ''Steinernema''. Although no ...

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 The Bergmann azlactone peptide synthesis is a classic organic synthesis process for the preparation of dipeptides. In the presence of a base, peptides are formed. s of N-carboxyanhydrides of amino acids with amino acid esters (). This reactio ...

is a classic

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

for the preparation of dipeptides.

Biosynthesis

Dipeptides are produced from

polypeptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides ...

s 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 es ...

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

dipeptidyl peptidase Dipeptidyl peptidase is a type of enzyme classified under EC 3.4.14. Types include: * Cathepsin C, dipeptidyl peptidase-1 * Dipeptidyl-peptidase II * DPP3, dipeptidyl peptidase-3 * DPP4, Dipeptidyl peptidase-4 * DPP6, dipeptidyl peptidase-6 * ...

. 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 Gastrin is a peptide hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach and aids in gastric motility. It is released by G cells in the pyloric antrum of the stomach, duodenum, and the pancreas. 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