Actinidains

Cysteine proteinases, EC 3.4.22.14, from kiwifruit — also called actinidins — with a protein-cutting specificity resembling papain’s. Commercially they serve as gentle meat tenderisers and digestive aids, breaking down proteins without the harshness of some alternatives. The catch is allergenicity: the major kiwifruit allergen Act d 1 is itself an actinidain, which is why kiwifruit allergy is clinically significant and cross-reacts with latex and certain pollens. Like all enzymes they lose activity with heat, so cooking ends their tenderising power — but heat does not reliably remove allergenic risk, and sensitive individuals should stay cautious.