Pyroglutamic acid (5-oxoproline) is produced and utilized in the gamma-glutamyl cycle. This cycle is needed to assist in the production and recycling of glutathione (GSH), a powerful antioxidant.
Glutathione is a tripeptide, consisting of glutamate, cysteine, and glycine. Using the gamma-glutamyl cycle, GSH is divided into cysteinyl glycine and a gammaglutamyl molecule which attaches to another amino acid for transport across a membrane or into a cell. Gammaglutamyl transferase then splits off that attached amino acid, and the glutamate becomes pyroglutamic acid (5-oxoproline).
Cysteinyl glycine is also broken down and transported into the cell as cysteine and glycine. The entire GSH molecule needs to be reformed intracellularly from pyroglutamic acid by recombining cysteine, glycine, and glutamic acid using GSH synthetase.
This enzymatic reformation requires cofactors such as ATP and magnesium.
References:
- Emmett M. Acetaminophen toxicity and 5-oxoproline (pyroglutamic acid): a tale of two cycles, one an ATP-depleting futile cycle and the other a useful cycle. Clin J Am Soc Nephrol. 2014;9(1):191-200.
- Metges CC, Yu YM, Cai W, et al. Oxoproline kinetics and oxoproline urinary excretion during glycine- or sulfur amino acid-free diets in humans. Am J Physiol Endocrinol Metab. 2000;278(5):E868-876.
- Persaud C, Forrester T, Jackson AA. Urinary excretion of 5-L-oxoproline (pyroglutamic acid) is increased during recovery from severe childhood malnutrition and responds to supplemental glycine. J Nutr. 1996;126(11):2823-2830.
Pyroglutamic Acid
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