Applications Ribonuclease A, and to a greater extent its oligomers and some homologs (such as onconase from frogs), have cytotoxic and cytostatic effects, particularly on cancer cells.This attribute has led to the development of onconase as a cancer therapeutic. Biochem/physiol Actions Ribonuclease A cleaves single stranded RNA after pyrimidine nucleotides. Unit Definition That amount of enzyme causing the hydrolysis of RNA at a rate such that k (velocity constant) equals unity at 25 °C and pH 5.0. Specific Activity:≥50 Kunitz u/mg