Serves as a reducing agent for the phage-induced ribonucleotide reductase, but not for the bacterial ones. This specificity may be the result of sequence differences around the redox-active disulfide bond. The oxidized form accepts electrons from bacterial glutathione and will, in turn, reduce other small disulfides. Can also be reduced by NADPH and by bacterial thioredoxin reductase. The disulfide bond functions as an electron carrier in the synthesis of deoxyribonucleotides from the corresponding ribonucleotide. Belongs to the glutaredoxin family. As it can also be reduced by thioredoxin reductase, it is also known as thioredoxin.