Micrococcal nuclease, also known as S7 nuclease or staphylococcal nuclease, is an extracellular nuclease first derived from Staphylococcus aureus. It is a non-specific endo-exonuclease that preferentially cleaves at the 5’ end to produce mononucleotides or oligonucleotides with terminal 3’ phosphates. It prefers single-stranded DNA and RNA, but can also digest double-stranded molecules over time. Its optimal pH is reported to be 9.2, strictly dependent on Ca2+, and inactivated by EGTA.