Single-strand-selective monofunctional uracil-DNA glycosylase(SMUG1) is an enzyme responsible for recognizing base lesions in the genome and initiating base excision DNA repair. SMUG1 participates in base excision repair by removing uracil from single- and double-stranded DNA. SMUG1 serves as a monofunctional DNA glycosylase specific for uracil(U) residues in DNA and has inclination for single-stranded DNA substrates. SMUG1 activity is greater against mismatches(U/G) than against matches(U/A).