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 some disulfides in a coupled system with glutathione reductase. Thioltransferase catalyzes cellular thiol-disulfide transhydrogenation reactions. It transfers reducing equivalents to cytosolic protein and nonprotein disulfides (By similarity). Belongs to the glutaredoxin family.