Figure 1.

Entry of NAC into the cell and incorporation of cysteine in the cycle of glutathione (GSH) synthesis. Glutathione is synthetized in a two-step ATP-dependent pathway from amino acids glutamate (Glu), cysteine (Cys), and glycine (Gly) under a gradual catalysis by enzymes glutamate-cysteine ligase (γ-glutamyl-cysteine synthase) (GCL) and GSH synthase (GSy). GSH is oxidated by glutathione peroxidase (GPx) into oxidized glutathione (GSSG), which may be reduced by glutathione reductase (GR) from GSSG back to GSH.