Hydrolyzes, with low efficiency, only single-stranded DNA and RNA without apparent specificity for bases (PubMed:17651368, PubMed:23620482). Endonuclease that recognizes and cleaves some mismatches with high efficiency, including heteroduplex double-stranded DNA; mostly efficient on T/G, A/G and G/G mismatches, less efficient for T/T and poorly efficient for C/C, A/A, T/C and A/C (PubMed:17651368). Endonucleolytic cleavage to 5'-phosphomononucleotide and 5'-phosphooligonucleotide end-products. Binds 3 divalent metal cations. Optimum pH is 8 with RNA and ssDNA as substrates. Monomer. Belongs to the nuclease type I family.