Actinidain

Actinidain (EC 3.4.22.14, actinidin, Actinidia anionic protease, proteinase A2 of Actinidia chinensis) is a type of cysteine protease enzyme found in fruits including kiwifruit (genus Actinidia), pineapple, mango, banana and papaya. This enzyme is part of the papain-like peptidase C1 family.

As a known allergen in kiwifruit, the enzyme is under preliminary research for its effect on tight junction proteins of intestinal epithelial cells.

Actinidain is commercially useful as a meat tenderizer and in coagulating milk for dairy products.