Releases mononucleotides from RNA in the order of 3'-GMP > 3'-UMP > 3'-AMP > 3'-CMP. a ribonucleotidyl-ribonucleotide-RNA + H2O = a 3'-end 3'-phospho-ribonucleotide-RNA + a 5'-end dephospho-ribonucleoside-RNA + H(+) Inhibited by Cu(2+) and Zn(2+). Optimum pH is 5.0. Belongs to the RNase T2 family.