Glutathione (GSH) is a tripeptide synthesized in the cytosol from precursor amino acids, L-glutamate, L-cysteine and glycine through two ATP-dependent steps catalyzed by the glutamate-cysteine ligase complex (comprising Gclc and Gclm) and glutathione synthases (Gss1 or Gss2). GSH can be transported to mitochondria and the ER, secreted, and is also found in the nucleus. GSH acts as an antioxidant and is involved in the regulation of cellular redox signaling (protein S-glutathionylation) and in xenobiotic detoxification. (Adapted from PMID:22995213.)