RNaza A is pyrimidine-specific endoribonuclease that acts on single-stranded RNA. RNaza A catalyzes cleavage of the phosphodiester bond between the 5′-ribose of a nucleotide and the phosphate group attached to the 3′-ribose of an adjacent pyrimidine nucleotide forming a 2′,3′-cyclic phosphate which may then be hydrolyzed to the corresponding 3′-nucleoside phosphate. A major application for RNase A is the removal of RNA from DNA preparations.