The enzyme serves as a mismatch repair enzyme that works to correct 7,8-dihydro-8-oxoguanine:adenine mispairs that arise in DNA when error-prone synthesis occurs past 7,8-dihydro-8-oxoguanine (GO) lesions in DNA. The enzyme excises the adenine of the mispair, producing an apurinic site sensitive to AP endonuclease activity. After removing the undamaged adenine the enzyme remains bound to the site to prevent EC 18.104.22.168
(MutM) from removing the GO lesion, which could lead to a double strand break. In vitro the enzyme is also active with adenine:guanine, adenine:cytosine, and adenine:7,8-dihydro-8-oxoadenine (AO) mispairs, removing the adenine in all cases.