Actinidain

Actinidain (, "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 tenderiser and in coagulating milk for dairy products. The denaturation temperature of actinidain is , lower than that of similar meat tenderising enzymes bromelain from pineapple and papain from papaya.