Gene Alias

Papain

Background

Papain, also known as papaya proteinase I, is a cysteine protease (EC 3.4.22.2) enzyme that is found in species of papaya, Carica papaya and Vasconcellea cundinamarcensis. The enzyme is found to be localized in the skin of papaya, and is collected from slashed unripe papayas as a crude latex. Papain is used in food, pharmaceutical, textile, and cosmetic industries. While it has been used for the treatment of inflammation and pain via topical administration, papain has also shown to have anthelmintic and tooth-whitening properties. When topically applied, papain induces an allergen-like inflammatory response via recruiting neutrophils, mast cells, and CD3-positive cells and by induction of a TH2-biased antibody response. In vitro, treatment of papain resulted in the breakdown of tight junctions of primary human keratinocytes that maintain the epithelial barrier integrity. These tight junction proteins include zonula occludens-1, claudin-4, and occludin. It is proposed that papain induces allergic responses via activation of TLR4, leading to an increase in neutrophils, CD3+ cells, mast cells, and CCL8-positive cells.