Papain is the best known cysteine protease. It was isolated in 1879 from the fruits of Carica papaya and was also the first protease of which a crystallographic structure was determined.
Papain is gathered by scoring the surface of the mature, unripe fruit after which the latex is collected and dried.
Papain is usually considered as a typical globular protein of modest size: its molecule weight is just 23,000 Da.
Upon heating it denatures in a rather narrow temperature range with extensive heat absorption.
The optimal activity of papain occurs art pH 5.8-7.0 and at temperature 50-57 °C when casein is used as the substrate.
It is a digestive enzyme that is used in meat tenderizers to breakdown tough meat fibers. South Americans have used papain to tenderize meat for centuries and it is now available in powdered meat tenderizers all over the word.
Papain is synthesized in the leaf mesophyll and transported to the pericarp of developing fruit via laticiferous ducts, the concentration of the protease is highest in the latex of unripe fruits.
What is papain?
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