RNase A, Ribonuclease A, is an endoribonuclease that cleaves the phosphodiester bonds of single strand RNA after pyrimidine nucleotides. It attacks at the 3′ phosphate end (For example pG-pG-pC-pA-pG will be cleaved to give pG-pG-pCp and A-pG). The highest activity is exhibited with single stranded RNA.