Figure 6. Metabolic pathways of glutathione synthesis, recycling, detoxification, and degradation; and a model for glutathione to serve as an oxidant for class III peroxidases during generation of ROS such as hydrogen peroxides.

Glu, Cys, γ-EC, Gly, and Cys-Gly represent glutamate, cysteine, γ-glutamylcysteine, glycine, and cysteinylglycine, respectively. γ-GCS, GS, GT, TPA, GST, GR, GPx, and III-Px represent γ-glutamylcysteine synthetases, glutathione synthetases, γ-glutamyltransferases, tripeptide aminopeptidases, glutathione S-transferases, glutathione reductases, glutathione peroxidases, and class III peroxidases, respectively. Blue arrows indicate direction of metabolite flow, whereas yellow arrows indicate transport of GSSG and GSH between cytosol and apoplast, where GSSG serves as an oxidant for class III peroxidases during ROS generation.