Pyroglutamic acid

Pyroglutamic acid
Preferred IUPAC name Pidolic acid
Systematic name 5-Oxopyrrolidine-2-carboxylic acid
Other names 5-Oxoproline 5-Oxo-proline
Identifiers
Abbreviations	Glp
CAS number	98-79-3 (2S) Y, 4042-36-8 (2R), 149-87-1 N
PubChem	7405 (2S), 439685 (2R), 499, 10534703 (2S)(3,4-3H2)
ChemSpider	7127 (2S) Y, 388752 (2R) Y, 485 Y, 8710094 (2S)(3,4-3H2) Y
UNII	SZB83O1W42 Y
EC number	205-748-3
DrugBank	DB03088
KEGG	C02237 N
MeSH	Pyrrolidonecarboxylic+acid
ChEBI	CHEBI:16010 N
ChEMBL	CHEMBL284718 N
RTECS number	TW3710000
Beilstein Reference	82134
Gmelin Reference	1473408
3DMet	B01549
Jmol-3D images	Image 1
SMILES O=C(O)[C@H]1NC(=O)CC1
InChI InChI=1S/C5H7NO3/c7-4-2-1-3(6-4)5(8)9/h3H,1-2H2,(H,6,7)(H,8,9) N Key: ODHCTXKNWHHXJC-UHFFFAOYSA-N N InChI=1S/C5H7NO3/c7-4-2-1-3(6-4)5(8)9/h3H,1-2H2,(H,6,7)(H,8,9)/t3-/m0/s1 InChI=1S/C5H7NO3/c7-4-2-1-3(6-4)5(8)9/h3H,1-2H2,(H,6,7)(H,8,9)/t3-/m0/s1 Key: ODHCTXKNWHHXJC-VKHMYHEASA-N
Properties
Molecular formula	C5H7NO3
Molar mass	129.11 g mol−1
Exact mass	129.042593095 g mol-1
Melting point	184 °C, 457 K, 363 °F
log P	-0.89
Acidity (pKa)	-1.76, 3.48, 12.76
Basicity (pKb)	15.76, 10.52, 1.24
Isoelectric point	0.94
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Pyroglutamic acid (also known as 5-oxoproline, pidolic acid, or pyroglutamate for its basic form) is an uncommon amino acid derivative in which the free amino group of glutamic acid cyclizes to form a lactam. It is found in many proteins including bacteriorhodopsin. N-terminal glutamine residues can spontaneously cyclize to become pyroglutamate. This is one of several forms of blocked N-terminals which present a problem for N-terminal sequencing using Edman chemistry, which requires a free primary amino group not present in pyroglutamic acid. The enzyme pyroglutamate aminopeptidase can restore a free N-terminus by cleaving off the pyroglutamate residue.

Pyroglutamic acid is also known as pidolic acid, exists as two distinct isomers:

• (2R) or (+) or l or D
• (2S) or (-) or d or L

Uses

The sodium salt of pyroglutamic acid – known either as sodium pyroglutamate or sodium pidolate – is used on the skin to retain moisture.^{[citation needed]}

Pyroglutamic acid is sold as a dietary supplement in the United States.^{[citation needed]}