An endonuclease from mouse cells specific for single-stranded DNA.

An endonuclease with a molecular weight of about 70000 (5-6S) was extensively purified from mouse ascites cells. The enzyme specifically attacks single-stranded DNA which is degraded mainly to oligonucleotides, with 5-10 residues. Supercoiled covalently closed circular phage DNA is converted to the linear relaxed form. The enzyme activity is highly sensitive to salt and can be stimulated by reagents lowering the dielectric constant of the buffer such as dimethylsulfoxide and glycerol.