Papain

Papain is a proteolytically active enzyme (protease/peptidase), which occurs in relatively high concentrations in the green skin and seeds of the papaya fruit (see melon tree below). Like other plant enzymes it is important for the defence against pests. Papain also has antibacterial, anti-inflammatory and antioxidant properties.

Industrially, papain is used as an additive to cleaning agents, for the depilation of animal skins during tanning, in textiles (prevents wool and silk from becoming matted). Nutritionally, the proteolytic properties of papain are used to "tenderise" meat.

Cosmetics: Papain is used in cosmetics. It acts as an antistatic agent, hair conditioning agent and skin care product. It is also used in peeling products. In this process proteins in the outer layers of the stratum corneum are broken down. Papain is also used in shampoos.

Naturopathy: As a therapeutic agent, papain is used in alternative medicine, for example for the enzymatic cleansing of chronic wounds .

Papain allergy: If people come into contact with the enzyme papain, allergic reactions such as rhinoconjunctivitis and bronchial asthma can occur in people who are predisposed to it (Tymoszuk D et al. 2016). Anaphylactic reactions have also been described. According to French and American studies, >1% of the population is sensitised (Monoret-Vautrin DA et al. 1985).

The complete molecular structure of papain was already discovered in 1969. Papain is structurally very similar to one of the most important allergens of the house dust and flour mites (p1, a major allergen of the house dust mite which belongs to the "papain-like cysteine protease family" and triggers immunological reactions through its proteolytic function).

Papain splits the tight junctions of the surface epithelium. In experimental animals the barrier function of the surface epithelium was lost. An analogous proteolytic property is also found in Der p1.

1. Benedé S et al (2014) Anaphylaxis induced by a drug containing lysozyme and papain: influence of papain on the IgE response. Int Arch Allergy Immunol 165:83-90
2. Iida H et al (2014) Epicutaneous administration of papain induces IgE and IgG responses in a cysteine protease activity-dependent manner. Allergol Int. 63: 219-226
3. Moneret-Vautrin DA et al (1985) Anaphylaxis to chymopapain induced by exertion. Presse Med 14:1614
   Morita H et al. (2015) An Interleukin-33-Mast Cell-Interleukin-2 Axis Suppresses Papain-Induced Allergic Inflammation by Promoting Regulatory T Cell Numbers. Immunity 43:175-186
4. Stremnitzer C et al (2015) Papain Degrades Tight Junction Proteins of Human Keratinocytes In Vitro and Sensitizes C57BL/6 Mice via the Skin Independent of its Enzymatic Activity or TLR4 Activation. J Invest Dermatol 135: 1790-180
5. Tymoszuk D et al(2016) Papain-induced occupational rhinoconjunctivitis and asthma - A case report.
   Med Pr 67:109-112.
6. Yi MH et al(2015) House dust mite allergen Der f 1 induces IL-8 in human basophilic cells via ROS-ERK and p38 signal pathways. Cytokines doi: 10.1016/j.cyto.2015.07.011