Endonuclease III (Nth) protein from E

coli acts as both N-glycosylase and a AP-lyase. The N-glycosylase activity releases damaged pyrimidines from double-stranded DNA, generating a basic (AP site). The AP-lyase activity of the enzyme cleaves 3′ to the AP site leaving a 5′ phosphate and a 3′ ring opened sugar. Some of the damaged bases recognized and removed by Endouclease III include urea, 5, 6 dihydroxythymine, thymine glycol, 5-hydroxy-5 methylhydanton, uracil glycol, 6-hydroxy-5, 6-dihdrothimine and methyltartronylurea.