|Preferred IUPAC name
|Systematic IUPAC name
|Molar mass||129.12 g·mol−1|
|Melting point||184 °C (363 °F; 457 K)|
|Acidity (pKa)||-1.76, 3.48, 12.76|
|Basicity (pKb)||15.76, 10.52, 1.24|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is: / ?)(|
Pyroglutamic acid (also known as PCA, 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 or glutamine cyclizes to form a lactam. 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. 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, also known as pidolic acid, exists as two distinct enantiomers:
- (2R) or D which happens to be (+) or d
- (2S) or L which happens to be (–) or l