Nuclease S1 (EC 3.1.30.1) is an endonuclease enzyme that splits single-stranded DNA (ssDNA) and RNA into oligo- or mononucleotides.
The enzyme hydrolyses single stranded region in duplex DNA such as loops or gaps.
Members of the S1/P1 family are found in both prokaryotes and eukaryotes and are thought to be associated in programmed cell death and also in tissue differentiation.
Additionally, the side chain of tryptophan located in the cavity in the active site and its backbone supports the action one of the zinc ions.
In molecular biology, it is used in removing single stranded tails from DNA molecules to create blunt ended molecules and opening hairpin loops generated during synthesis of double stranded cDNA.