Specifically hydrolyzes both 8-oxo-deoxyguanosine triphosphate (8-oxo-dGTP) and 8-oxo-guanosine triphosphate (8-oxo-GTP) to the related monophosphates, thereby cleaning up the nucleotide pools and preventing misincorporation of 8-oxoGua into DNA and RNA. It prevents replicational errors by removing an oxidatively damaged form of guanine (8-oxo-dGTP) from DNA and the nucleotide pool. 8-oxo-dGTP can be inserted opposite dA and dC residues of template DNA with almost equal efficiency thus leading to A.T to G.C transversions. MutT may also ensure transcriptional fidelity, removing 8-oxo-GTP from the ribonucleotide triphosphate pool. However, due to the lower efficiency of RNA polymerase 8-oxo-GTP incorporation, MutT is probably not a major contributor to transcriptional fidelity. It also hydrolyzes 8-oxo-dGDP and 8-oxo-GDP to their monophosphate form. In vitro, can also use dGTP, dGDP and other various nucleoside di- and triphosphates, with much lower efficiency. Works cooperatively with MutM and MutY to prevent accumulation in the DNA of oxidized guanine residues.

> 90% as determined by SDS-PAGE.