Pyroglutamic acid

Pyroglutamic acid
Names
	Preferred IUPAC name 5-Oxoproline
	Systematic IUPAC name 5-Oxopyrrolidine-2-carboxylic acid
	Other names 2-Pyrrolidone-5-carboxylic acid; Pidolic acid; 5-Oxo-proline;
Identifiers
CAS Number	149-87-1 (R/S) ; 4042-36-8 (R) ; 98-79-3 (S) ;
3D model (JSmol)	Interactive image;
3DMet	B01555;
Abbreviations	Glp
Beilstein Reference	82134
ChEBI	CHEBI:16010 (R/S) ; CHEBI:16924 (R); CHEBI:18183 (S);
ChEMBL	ChEMBL284718 ;
ChemSpider	485 (R/S) ; 388752 (R) ; 7127 (S) ;
DrugBank	DB03088 ;
ECHA InfoCard	100.005.227
EC Number	205-748-3;
Gmelin Reference	1473408
IUPHAR/BPS	4703;
KEGG	C02237 ;
MeSH	Pyrrolidonecarboxylic+acid
PubChem CID	499 (R/S); 439685 (R); 7405 (S);
RTECS number	TW3710000;
UNII	6VT1YZM21H (R/S) ; SZB83O1W42 (S) ;
CompTox Dashboard (EPA)	DTXSID80859174 ;
	InChI InChI=1S/C5H7NO3/c7-4-2-1-3(6-4)5(8)9/h3H,1-2H2,(H,6,7)(H,8,9) Key: ODHCTXKNWHHXJC-UHFFFAOYSA-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;
	SMILES O=C(O)[C@H]1NC(=O)CC1;
Properties
Chemical formula	C5H7NO3
Molar mass	129.115 g·mol−1
Melting point	184 °C (363 °F; 457 K)
log P	-0.89
Acidity (pKa)	-1.76, 3.48, 12.76
Basicity (pKb)	15.76, 10.52, 1.24
Isoelectric point	0.94
Related compounds
Related compounds	proline; 2-Pyrrolidone
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Pyroglutamic acid (also known as PCA, 5-oxoproline, pidolic acid) is a ubiquitous but understudied natural amino acid derivative in which the free amino group of glutamic acid or glutamine cyclizes to form a lactam.^[1] The names of pyroglutamic acid conjugate base, anion, salts, and esters are pyroglutamate, 5-oxoprolinate, or pidolate.

It is a metabolite in the glutathione cycle that is converted to glutamate by 5-oxoprolinase. Pyroglutamate is found in many proteins including bacteriorhodopsin. N-terminal glutamic acid and glutamine residues can spontaneously cyclize to become pyroglutamate, or enzymatically converted by glutaminyl cyclases.^[2] This is one of several forms of blocked N-termini 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.^[3]

Pyroglutamic acid exists as two distinct enantiomers:

(2R) or D which happens to be (+) or d
(2S) or L which happens to be (–) or l

^ Cite error: The named reference throwing was invoked but never defined (see the help page).
^ Schilling, Stephan; Wasternack, Claus; Demuth, Hans-Ulrich (1 August 2008). "Glutaminyl cyclases from animals and plants: a case of functionally convergent protein evolution". Biological Chemistry. 389 (8): 983–91. doi:10.1515/BC.2008.111. PMID 18979624. S2CID 24074284.
^ Podell, David N.; Abraham, George N. (March 1978). "A technique for the removal of pyroglutamic acid from the amino terminus of proteins using calf liver pyroglutamate amino peptidase". Biochemical and Biophysical Research Communications. 81 (1): 176–185. doi:10.1016/0006-291X(78)91646-7. PMID 26343.

[throwing-1] Cite error: The named reference throwing was invoked but never defined (see the help page).

[2] Schilling, Stephan; Wasternack, Claus; Demuth, Hans-Ulrich (1 August 2008). "Glutaminyl cyclases from animals and plants: a case of functionally convergent protein evolution". Biological Chemistry. 389 (8): 983–91. doi:10.1515/BC.2008.111. PMID 18979624. S2CID 24074284.

[3] Podell, David N.; Abraham, George N. (March 1978). "A technique for the removal of pyroglutamic acid from the amino terminus of proteins using calf liver pyroglutamate amino peptidase". Biochemical and Biophysical Research Communications. 81 (1): 176–185. doi:10.1016/0006-291X(78)91646-7. PMID 26343.

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