Catalysis of the endonucleolytic cleavage of RNA to 3'-phosphomononucleotides and 3'-phosphooligonucleotides ending in C-P or U-P with 2',3'-cyclic phosphate intermediates.
RNase A activity; RNase I activity; S-genotype-assocd. glycoproteins; SLSG glycoproteins; endoribonuclease I; gene S glycoproteins; gene S locus-specific glycoproteins; pancreatic RNase activity; ribonuclease I activity