actinidin

Actinidin is a cysteine protease enzyme found in kiwifruit. Its primary function is to break down proteins into smaller peptides and amino acids. This enzymatic activity is responsible for some of the desirable characteristics of kiwifruit, such as its tenderizing effect on meat and its role in digestion. Actinidin belongs to the papain family of proteases, sharing structural and functional similarities with other plant-derived enzymes like papain from papaya and bromelain from pineapple.

The enzyme is composed of a single polypeptide chain and requires a thiol group for its catalytic activity. It functions optimally within a specific pH range and temperature, which are typical of the environment within the kiwifruit. In the human digestive system, actinidin can contribute to protein breakdown, potentially aiding in nutrient absorption. However, for some individuals, the presence of actinidin can also cause adverse reactions, such as oral allergy syndrome, characterized by itching or tingling in the mouth and throat.

In culinary applications, actinidin is utilized as a natural meat tenderizer. When meat is marinated with kiwifruit, the actinidin breaks down tough muscle fibers, resulting in a more tender texture. It is also sometimes used in the production of dietary supplements aimed at improving protein digestion. Research continues to explore the therapeutic and commercial applications of actinidin, investigating its potential in various fields beyond food processing and digestion.