Proline ( pyrrolidine-α-carboxylic acid ) is a heterocyclic amino acid in which the nitrogen atom is a part of the secondary, rather than primary, amine (in connection with which proline is more correctly called an amino acid) [1] . It exists in two optically isomeric forms - L and D, as well as in the form of a racemate .
| Proline | |
|---|---|
 | |
 | |
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| General | |
| Systematic name | L-pyrrolidin-2- carbon acid |
| Abbreviations | Pro, Pro, P CCU, CCC, CCA, CCG |
| Chem. formula | C₅H₉NO₂ |
| Rat formula | C 5 H 9 NO 2 |
| Physical properties | |
| Molar mass | 115.13 g / mol |
| Density | 1.35-1.38 g / cm³ |
| Thermal properties | |
| T. melt. | 221 ° C |
| Chemical properties | |
| pK a | 1.99 10.60 |
| Classification | |
| Reg. CAS number | [147-85-3] |
| PubChem | |
| Reg. EINECS number | 205—702-2 |
| Smiles | |
| Inchi | |
| RTECS | |
| Chebi | , , , , and |
| ChemSpider | |
L-Proline is one of twenty proteinogenic amino acids. It is believed that proline is part of the proteins of all organisms. Especially rich in proline is the main protein of connective tissue - collagen . As part of the proteins, the nitrogen atom in the proline molecule is not bound to a hydrogen atom, so the X-Pro peptide moiety cannot be a hydrogen donor in the formation of a hydrogen bond. Having a conformationally rigid structure, proline strongly bends the peptide chain. Plots of proteins with a high proline content often form the secondary structure of a type II polyproline helix.
Physical and chemical properties
It is a colorless, easily soluble in water crystals, melting at a temperature of about 220 ° C. It is also soluble in ethanol , worse in acetone and benzene , insoluble in diethyl ether .
In the body, proline is synthesized from glutamic acid .
Proline, like hydroxyproline , unlike other amino acids, does not form purple Rueman with ninhydrin , but gives a yellow color.
In the composition of collagen, proline with the participation of ascorbic acid is oxidized to hydroxyproline. Alternating residues of the proline and hydroxyproline molecules contribute to the creation of a stable three-helix structure of collagen , which gives the molecule strength.
Laboratory Proline Synthesis
A racemic mixture of L- and D-proline can be obtained from malonic acid diethyl ether and acrylonitrile [2] :
Notes
- ↑ Kukhta V.K., Oletsky Z.I., Taganovich A.D. Biological chemistry: textbook / ed. A. D. Taganovich - Minsk: Asar, M.: BINOM Publishing House, 2008. - 8 p.
- ↑ Vogel Practical Organic Chemistry 5th edition