Proline

Proline

Names
IUPAC name Proline
Systematic IUPAC name Pyrrolidine-2-carboxylic acid
Identifiers
CAS Number	609-36-9 Y 344-25-2 (R) Y 147-85-3 (S) Y
3D model (Jmol)	Interactive image Interactive image
Beilstein Reference	80812
ChEBI	CHEBI:26271 Y
ChEMBL	ChEMBL72275 Y
ChemSpider	594 Y 8640 (R) Y 128566 (S) Y
DrugBank	DB00172 N
ECHA InfoCard	100.009.264
EC Number	210-189-3
Gmelin Reference	26927
KEGG	C16435 Y
MeSH	Proline
PubChem	614 8988 (R) 145742 (S)
RTECS number	TW3584000
UNII	DCS9E77JPQ Y
InChI InChI=1S/C5H9NO2/c7-5(8)4-2-1-3-6-4/h4,6H,1-3H2,(H,7,8) Y Key: ONIBWKKTOPOVIA-UHFFFAOYSA-N Y InChI=1/C5H9NO2/c7-5(8)4-2-1-3-6-4/h4,6H,1-3H2,(H,7,8)
SMILES OC(=O)C1CCCN1 C1CC(NC1)C(=O)O
Properties
Chemical formula	C5H9NO2
Molar mass	115.13 g·mol−1
Appearance	Transparent crystals
Melting point	205 to 228 °C (401 to 442 °F; 478 to 501 K) (decomposes)
Solubility	1.5g/100g ethanol 19 degC
log P	-0.06
Acidity (pKa)	1.99 (carboxyl), 10.96 (amino)
Hazards
Safety data sheet	See: data page
S-phrases	S22, S24/25
Supplementary data page
Structure and properties	Refractive index (n), Dielectric constant (εr), etc.
Thermodynamic data	Phase behaviour solid–liquid–gas
Spectral data	UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Proline (abbreviated as Pro or P; encoded by the codons CCU, CCC, CCA, and CCG) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated >NH₂⁺ form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO⁻ form under biological conditions), and a side chain pyrrolidine, classifying it as a nonpolar(at physiological pH), aliphatic amino acid. It is non-essential in humans, meaning the body can synthesize it from the non-essential amino acid L-glutamate.

Proline is the only proteinogenic amino acid with a secondary amine, in that the alpha-amino group is attached directly to the side chain, making the α carbon a direct substituent of the side chain.

Proline was first isolated in 1900 by Richard Willstätter who obtained the amino acid while studying N-methylproline. The year after Emil Fischer published the synthesis of proline from phthalimide propylmalonic ester. The name proline comes from pyrrolidine, one of its constituents.

Proline is biosynthetically derived from the amino acid L-glutamate. Glutamate-5-semialdehyde is first formed by glutamate 5-kinase (ATP-dependent) and glutamate-5-semialdehyde dehydrogenase (which requires NADH or NADPH). This can then either spontaneously cyclize to form 1-pyrroline-5-carboxylic acid, which is reduced to proline by pyrroline-5-carboxylate reductase (using NADH or NADPH), or turned into ornithine by ornithine aminotransferase, followed by cyclisation by ornithine cyclodeaminase to form proline.