7,8-dihydro-8-oxoguanine triphosphatase The enzyme 8-oxo-7,8-dihydrodeoxyguanosine triphosphatase (8-oxo-dGTPase) is present in a variety of organisms, where it plays an important role in the control of spontaneous mutagenesis [<cite idref="PUB00008130"/>]. The enzyme degrades 8-oxoguanine- containing deoxyribonucleoside triphosphate, a potentially mutagenic substrate for DNA synthesis, to the corresponding monophosphate, thereby preventing misincorporation of 8-oxo-dGTP into DNA [<cite idref="PUB00008130"/>]. <p> 8-oxo-dGTPase is an 18kDa protein containing 156 amino acid residues. The amino acid sequence shares a degree of similarity with the MutT domain of the <taxon tax_id="562">Escherichia coli</taxon> MutT protein, which has a distinct 8-oxo-dGTPase activity [<cite idref="PUB00002808"/>]. When human cDNA is expressed in E. coli mutT- mutant cells, there is a significant amount of 8-oxo-dGTPase activity and a reduced frequency of spontaneous mutation. Human 8-oxo-dGTPase is thought to protect genetic information from the untoward effects of endogenous oxygen radicals [<cite idref="PUB00002808"/>].</p>