Aspergillus nuclease S1

Aspergillus nuclease S1
EC number
CAS number 37288-25-8
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum

Aspergillus nuclease S1 is an endonuclease enzyme derived from Aspergillus oryzae that splits single-stranded DNA (ssDNA) and RNA into oligo- or mononucleotides. This enzyme catalyses the following chemical reaction

Endonucleolytic cleavage to 5'-phosphomononucleotide and 5'-phosphooligonucleotide end-products

Although its primary substrate is single-stranded, it can also occasionally introduce single-stranded breaks in double-stranded DNA or RNA, or DNA-RNA hybrids. The enzyme hydrolyses single stranded region in duplex DNA such as loops or gaps.


Alternative names include EC, endonuclease S1 (Aspergillus), single-stranded-nucleate endonuclease, deoxyribonuclease S1, deoxyribonuclease S1, nuclease S1, Neurospora crassa single-strand specific endonuclease, S1 nuclease, single-strand endodeoxyribonuclease, single-stranded DNA specific endonuclease, single-strand-specific endodeoxyribonuclease, single strand-specific DNase and Aspergillus oryzae S1 nuclease.


Aspergillus nuclease S1 is a monomeric protein of a molecular weight of 38 kilodalton. It requires Zn2+ as a cofactor and is relatively stable against denaturing agents like urea, SDS, or formaldehyde. The optimum pH for its activity lies between 4-4.5. Aspergillus nuclease S1 is known to be inhibited somewhat by 50 μM ATP and nearly completely by 1 mM ATP.[1][2] 50% inhibition has been shown at 85 μM dAMP and 1 μM dATP but uninhibited by cAMP.[3]


Aspergillus nuclease S1 is used in the laboratory as a reagent in nuclease protection assays. 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.


  1. Yang, Xinjian; Fang Pu; Jinsong Ren; Xiaogang Qu (2011). "DNA-templated ensemble for label-free and real-time fluoresence turn-on detection of enzymatic/oxidative cleavage of single-stranded DNA". Chemical Communications. 47: 8133–8135. doi:10.1039/c1cc12216a.
  2. Wrede, Paul; Alexander Rich (1979). "Stability of the unique anticodon loop conformation of E.Col tRNAMetf". Nucleic Acids Research. 7 (6). doi:10.1093/nar/7.6.1457.
  3. Wiegand, RC; GN Godson; CM Radding (1975). "Specificity of the S1 nuclease from Aspergilus oryzae". The Journal of Biological Chemistry. 250 (22).
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