Pyroglutamic acid (also known as PCA, 5-oxoproline, pidolic acid, or pyroglutamate for its basic form) is a ubiquitous but little studied natural 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, or enzymatically converted by glutaminyl cyclases.

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.

1.Pyroglutamic acid is one of the main components of the skin's natural moisturizing factor, and its moisturizing ability far exceeds that of glycerin and propylene glycol. It is non-toxic and non-irritating, and is an excellent raw material for modern skin care and hair care cosmetics.

2.Pyroglutamic acid also inhibits the activity of tyrosine oxidase, thereby preventing the deposition of "melanoid" substances in the skin and whitening the skin.

3.It has a softening effect on keratin and can be used in nail cosmetics.

4.In addition to its application in cosmetics, L-pyroglutamic acid can also form derivatives with other organic compounds, which have special effects in surface activity, transparent light and so on.

5.Can also be used as a surfactant for detergents; chemical reagents for the resolution of racemic amines; organic intermediates.