Papain, the proteolytic enzyme used as a digestive aid, comes from the latex of the papaya plant, Carica papaya. The latex is especially abundant in unripe green fruit and is collected by scoring the fruit’s skin.
Papain is a cysteine protease, meaning it breaks peptide bonds in proteins. That activity explains its use in digestive preparations and also its long-standing culinary role as a meat tenderizer. Papaya latex is collected, dried, and processed into a crude enzyme material before purification.
Papain is not the same thing as bromelain, another plant protease associated with pineapple. That is a common quiz mix-up because both enzymes break down proteins and appear in food or supplement discussions. Papaya also contains other proteolytic enzymes, including chymopapain.
The enzyme has uses beyond digestion and cooking. It has been used in laboratory cell dissociation and in some topical debriding products. However, papain can trigger allergic reactions, particularly in some people with latex sensitivity, so “natural” does not automatically mean risk-free.