dADP, dGDP, dCDP, dUDP ADP, GDP, CDP, UDP NDP + reduced glutaredoxin => dNDP + oxidized glutaredoxin + H2O Cytosolic ribonucleotide reductase catalyzes the reduction of adenine, guanine, cytidine, and uridine ribonucleoside 5'-diphosphates to form the corresponding deoxyribonucleoside 5'-diphosphates, coupled to the oxidation of glutaredoxin (Eklund et al. 2001). Ribonucleotide reductase is a tetramer of two large and two small subunits (Shao et al. 2004; Zhou et al. 2005). The overall activity of the enzyme is regulated allosterically: ATP binding is stimulatory while dATP binding is inhibitory (Reichard et al. 2000).<p>The reducing equivalents needed for ribonucleotide reductase activity can be provided by either of two small proteins, glutaredoxin and thioredoxin (Holmgren 1989; Sun et al. 1998). Both are re-reduced with NADPH as the donor of reducing equivalents, and so are active in catalytic amounts. The relative contributions of glutaredoxin and thioredoxin in vivo are unknown. Pubmed10884394 Pubmed11796141 Pubmed14729598 Pubmed16373698 Pubmed2668278 Pubmed9677297 Reactome Database ID Release 43111742 Reactome, http://www.reactome.org ReactomeREACT_375 Reduction of cytosolic ribonucleoside 5'-diphosphates to deoxyribonucleoside 5'-diphosphates (glutaredoxin)