Papain

Papain is a **cysteine protease enzyme** (EC 3.4.22.2) found predominantly in the latex of the papaya fruit (*Carica papaya*) and also in mountain papaya (*Vasconcellea cundinamarcensis*)[1][2][3][4][5][7]. It consists of 212 amino acids with a catalytic triad featuring cysteine-25, histidine-159, and asparagine-158, enabling it to cleave peptide bonds across a broad range of substrates, with a preference for hydrophobic amino acids at the P2 position[5]. Papain serves diverse biological and industrial roles, including use as a meat tenderizer, digestive aid, and component in enzymatic wound debridement therapies[1][2][7]. It can cleave immunoglobulins into functional domains (Fab and Fc), enhancing its relevance in immunological applications[5]. Therapeutically, papain has been explored primarily for topical anti-inflammatory, digestive, and proteolytic (debriding) purposes, though FDA approval and regulatory status for these indications remain limited or withdrawn due to concerns around efficacy, safety, and potential adverse reactions[5]. Papain is the prototypical member of the papain-like cysteine protease family, which includes many medically and biologically significant enzymes encountered across species[1][4].

Other names

Papaya proteinase IPapaya peptidase IPPI

Hydrolysis of peptide bonds (proteolysis), Debridement via breakdown of necrotic tissue proteins, Cleavage of antibodies into Fab and Fc fragments