Proline

  • L-proline
  • ( S)-proline
  • D -proline
  • (R )-proline
  • (2S)- pyrrolidine - 2-carboxylic acid
  • (2S) -1,3,4,5 -tetrahydro- 2H -pyrrole-2 -carboxylic acid
  • (2S)- azacyclopentan - 2-carboxylic acid
  • (2S)- azolidine - 2-carboxylic acid
  • Abbreviations: Pro ( Three letter code)
  • P ( single letter code )

V06

Colorless solid with an amine-like odor

Fixed

1.35-1.38 gcm -3 ( 25 ° C)

Decomposition: 220-222 ° C (D - and L-form ) 210 ° C ( racemate)

  • PKCOOH: 1.99
  • PKNH2: 10.60 ( each at 25 ° C)
  • Very well in water (1500 g · l-1 at 20 ° C)

> 5110 mg · kg -1 ( LD50, rat, oral)

Template: Infobox chemical / molecular formula search available

L-proline, abbreviated Pro or P [ systematic name ( S)- pyrrolidine -2-carboxylic acid] is a non-essential proteinogenic heterocyclic secondary α -amino acid and is used for its biosynthesis from pyrroline - 2-carboxylic acid [ precisely, (S) - 3,4-dihydro -2H -pyrrole-2 -carboxylic acid ] as sometimes erroneously imino ( a now obsolete classification ) respectively.

If in this text or in the scientific literature " proline " without further suffix (prefix ) is mentioned, L- proline is meant.

History

The name is derived from proline Emil Fischer and is derived from pyrrolidine.

Occurrence

Within proteins it occurs both in cis and in trans -bonded configuration. L- proline has a significant influence on the folding of proteins because it can disrupt α - helices and β -sheets due to the frequently occurring cis- amide bond such as glycine. It can also make your own designs, which often act as a signal sequence for other proteins.

Biosynthesis

For the biosynthesis including structural formulas, see section External links

L- proline is produced biochemically from L- glutamate. For this purpose, a molecule of ATP and two molecules of reducing equivalents in the form of NADPH are required in total.

L- proline is the precursor of L- hydroxyproline, which is formed with the participation of vitamin C after incorporation into collagen and its mechanical properties determined ( deficiency disease: scurvy ). Catalyzed by a hydroxylase Prolylreste be modified depending on their position in the protein, either the β - or γ - atom of the Tetrahydropyrrolringes.

Properties

Proline is present predominantly as the "inner salt " or zwitterion, whose formation can be explained by the fact that the proton of the carboxyl group migrates to the lone pair of the nitrogen atom of the amino group.

In an electric field, the zwitterion migrates not because it is not loaded as a whole. Strictly speaking, this is at the isoelectric point ( a certain pH value) of the case, wherein the proline has its lowest solubility in water.

Characterized in that the nitrogen atom of proline is not connected in the peptide group having a hydrogen atom, any of hydrogen bonding may be formed. At such points of a polypeptide chain occurs a disturbance of the secondary structure ( kink or curvature ).

Other features include:

  • Side chain: hydrophobic
  • Van -der- Waals volume: 90 Å3
  • Lipid solubility: Log P = -1.6

Functions

L- proline is in the human body, for example, for the formation of collagen, the protein consisting of the connective tissue and bone, are required. Further, it is referred to as a " helix breaker " and is often found at the junction of an alpha -helical secondary structure to another (often random coil ) again. L- proline is used as a biomarker in ecotoxicology, eg for drought stress, salt stress, as it is increasingly produced by plants when the water balance is coming under stress. L- proline as the cyclic amino acid acts as a buffer against some ions which might otherwise restrict the enzyme activities in the cytoplasm.

Chemical use

Enantiopure proline as an element of the chiral pool starting material for the synthesis of Evans' auxiliary, the CBS reagent of the Enders reagent ( RAMP / SAMP ) and is a much used catalyst in organocatalysis. The literature on the use of ( S) - or (R )-proline and its derivatives in stereoselective synthesis is extensive. An L- proline derivative is used as a chiral selector for enantioselective thin layer chromatography. The therapeutically and economically significant drug captopril is synthesized from L- proline.

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