Papain, also known as papaya proteinase I, is a cysteine protease () enzyme present in papaya (Carica papaya) and mountain papaya (Vasconcellea cundinamarcensis).
Papain family
Papain belongs to a family of related proteins with a wide variety of activities, including endopeptidases, aminopeptidases, dipeptidyl peptidases and enzymes with both exo- and endo-peptidase activity. Members of the papain family are widespread, found in baculovirus, eubacteria, yeast, and practically all protozoa, plants and mammals. Papain-like cysteine proteinases are essentially synthesised as inactive proen...