Salt Active Nuclease (SAN)

Salt active nuclease has been used to remove DNA during protein expression and purification.

Salt active nuclease (SAN) is a general, unspecific endonuclease that cleaves double-stranded and single-stranded DNA, and RNA. SAN is active at above neutral pH.  Unlike other nucleases, however, it has optimum activity at high concentrations of salt at high pH.  These qualities make SAN ideal for removal of DNA from cell extracts and protein samples.  The end-products upon complete degradation of DNA consist of a majority of 5 nucleotide
oligos.  The enzyme degrades DNA vs. RNA in a ratio of 10:1.

SAN is highly active over the temperature range 10-40 °C. The optimal NaCl-concentration for activity is 0.5 M.  However, SAN is active in low salt buffers.  1 M NaCl is not recommended for use of SAN.  Mg2+ (>1 mM) is required for activity.  The pH working range is above neutral pH, with an optimal range between pH 8.5-9.5

Physical form:  Solution in 25 mM Tris-HCl (pH 7.5), 5 mM MgCl2, 0.5 M NaCl, 0.01% Triton, and 50% (v/v) glycerol

Unit definition:  One unit (U) is defined as an increase in absorbance at 260 nm of 1 Absorbance Unit in 30 minutes at 37 ºC, using 50 μg/ml calf thymus DNA in a buffer with 25 mM Tris-HCl (pH 8.5, 25 ºC), 5 mM MgCl2, and 500 mM NaCl.

One unit (U) is defined as an increase in absorbance at 260 nm of 1 absorbance unit (AU) in 30 minutes at 37 °C, using 50 μg/ml calf thymus DNA in a buffer with 25 mM Tris-HCl (pH 8.5, 25 °C), 5 mM MgCl₂, and 500 mM NaCl.