Specificity
g-glutamylcysteine synthetase (g-GCS) is the rate limiting enzyme for glutathione (L-g-glutamyl-L-cysteinylglycine, GSH) synthesis. GSH is ubiquitous in mammalian cells as a vital intra- and extracellular protective antioxidant. g-GCS is a heterodimer of a heavy catalytic subunit and a light regulatory subunit that is responsive to inflammation, phenolic antioxidants, heat shock, oxidants and cytokines. The human g-GCS gene encoding the 367 amino acid catalytic subunit maps to chromosome 6p12. The human g-GCS gene encoding the regulatory subunit maps to chromosome 1p22.1. The two subunits of g-GCS form a heterodimeric zinc metalloprotein that gains activity through formation of a reversible disulfide bond.