The papain also is known as papaya proteinase or papaya enzyme, It is a low-specificity proteolytic enzyme extracted from the milky juice of unripe papaya (Carica papaya) by biotechnology. Its appearance is light yellow to white powder, slightly hygroscopic, soluble in water and glycerin, the aqueous solution is colorless or milky white, almost insoluble in organic solvents such as ethanol, chloroform and ether. Green papaya extract papain contains both strong protein hydrolysis catalytic activity and curds and lysozyme activity, also with the function of lipolysis and protein synthesis, mainly catalytic protein hydrolysis, also can break down the small peptide, can be used for improving the nutritional value or function of the plants and the animal protein The active center of papain contains cysteine, which belongs to the thiol protease. It has high enzyme activity, good thermal stability, natural hygiene and safety, widely used in food,medicine, feed, daily chemical, leather and textile industries.