Multifunctional enzyme with glutathione-dependent oxidoreductase, glutathione peroxidase and glutathione S-transferase (GST) activity. The disulfide bond functions as an electron carrier in the glutathione-dependent synthesis of deoxyribonucleotides by the enzyme ribonucleotide reductase. In addition, it is also involved in reducing cytosolic protein- and non-protein-disulfides in a coupled system with glutathione reductase. May play a role in protection against oxidative stress caused by superoxide in vivo by regulating the redox state of the protein sulfhydryl groups. Up-regulation of expression first detected at 24 hours after exposure to copper and reaches to a maximum after 7 days. Up-regulation of expression reaches to a maximum at 12 hours after exposure to paraquat and returns to basal levels within 24 hours. Belongs to the glutaredoxin family.