Base excision repair (BER) glycosylase that initiates repair of A:oxoG to C:G by removing the inappropriately paired adenine base from the DNA backbone, generating an abasic site product. 8-oxoguanine (oxoG) is a genotoxic DNA lesion resulting from oxidation of guanine; this residue is misread by replicative DNA polymerases, that insert adenine instead of cytosine opposite the oxidized damaged base. Shows a powerful dicrimination of A versus C, since it does not cleave cytosine in oxoG:C pairs. May also be able to remove adenine from A:G mispairs, although this activity may not be physiologically relevant. Hydrolyzes free adenine bases from 7,8-dihydro-8-oxoguanine:adenine mismatched double-stranded DNA, leaving an apurinic site. Binds 1 [4Fe-4S] cluster. The cluster has a structural role. Expressed during exponential growth. Expressed as both a monocistronic transcript and a mutY-fabL-sspE transcript. Cells lacking this gene have a 100-fold increased spontaneous mutation frequency. A double mutM/mutY disruption has a 1000-fold increased spontaneous mutation frequency (PubMed:12483591). Triple ytkD/mutM/mutY disrupted strains show increased mutation rates during exponential and stationary phase (PubMed:19011023). Belongs to the Nth/MutY family.