dipeptide
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A dipeptide is an
organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, ...
derived from two
amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's ability to Catenation, c ...
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 is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are s ...
, an
artificial sweetener A sugar substitute is a food additive that provides a sweetness, sweet taste like that of sugar while containing significantly less food energy than sugar-based sweeteners, making it a zero-calorie (non-nutritive) or low-calorie sweetener. Artifi ...
. 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

is produced commercially as an artificial sweetener.


Commercial value

About six dipeptides are of commercial interest. *
Aspartame Aspartame is an artificial non-saccharide is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are s ...
(''N''-L-α-aspartyl-L-phenylalanine 1-methyl ester) is an artificial
sweetener A sugar substitute is a food additive that provides a sweetness, sweet taste like that of sugar while containing significantly less food energy than sugar-based sweeteners, making it a zero-calorie (non-nutritive) or low-calorie sweetener. Artif ...
. * Carnosine (''beta''-alanyl-L-histidine) and (''beta''-alanyl-''N''-methyl histidine) are highly concentrated in
muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cate ...

muscle
and brain tissues. They are used in sports medicines. *, 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 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 complex, supramolecular scale for industrial purposes. The earliest, widespread description of nanotechnology referred to the particul ...

nanotechnology
* (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. *Glorin (''N''-propionyl-γ-L-glutamyl-L-ornithine-δ-lac ethyl ester) is a chemotactic peptide, chemotactic dipeptide for the slime mold ''Polysphondylium violaceum''. *Barettin (cyclo-[(6-bromo-8-en-tryptophan)-arginine]) is a cyclic peptide, cyclic dipeptide from the marine sponge ''Geodia barretti''. *Pseudoproline *Dialanine is commonly used as a model in Molecular dynamics.


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)CO2CH3RCH(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 protecting group, 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 enzyme 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)

Image:Retosiban structure.svg, 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


External links


An introduction to dipeptides
at PeptideGuide. {{Peptides Dipeptides,