Purification and Further Properties of Single‐Strand‐Specific Nuclease from Aspergillus oryzae

A simple scheme has been devised for the purification of Aspergillus nuclease S 1 from commercially available crude amylase powder. Five purification steps yield 90% pure nuclease with an overall yield of 27%. The enzyme is shown to be absolutely specific for single‐stranded nucleic acids. It degrades both DNA and RNA. The nuclease exhibits a sharp pH optimum at pH 4.2 and is active in low concentrations of dodecylsulfate. Aspergillus nuclease S 1 is a metalloprotein of molecular weight 32000. The utility of this nuclease for measuring annealing of labeled DNA is discussed.