核糖核酸酶A，来源牛胰脏

从牛胰腺中提取出来的聚集型和游离型的RNA蛋白酶A，是核糖核酸内切酶，含有124个氨基酸残基。这种酶能特定催化和分解嘧啶核苷酸，使其裂解产物的5'-核糖核苷酸与3'-核糖核苷酸之间通过磷酸二酯键连接起来。此裂解产物可形成2，3-环磷酸酯，然后水解成相应的3'-核苷磷酸。

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.