Properties of Papain

Papain is a mixture of proteases refined from the papaya plant (Carica papaya) and appears as a white to light brown amorphous powder or granules. It is slightly hygroscopic and has a characteristic smell of hydrogen sulfide. It is somewhat soluble in water and glycerin, but insoluble in ether, ethanol, and chloroform. The aqueous solution is colorless to light yellow and can sometimes appear milky. Its optimal pH ranges from 5.0 to 8.0, with an ideal temperature of 65 °C; it is sensitive to denaturation.

Papain contains several proteases, including papain itself, papaya latex protease, and proteolytic enzymes. Papain is a thiol protease with relatively broad specificity, capable of breaking down more types of protein than pancreatic protease. It consists of a single polypeptide chain made up of 211 amino acid residues, with a molecular weight of 23,000 and an isoelectric point (pI) of 9.6. Activators include cysteine, sulfides, bisulfites, and EDTA, while inhibitors include thiol reagents and hydrogen peroxide. Papain comprises about 10% of soluble proteins; papaya latex protease makes up approximately 45% with a molecular weight of 36,000, and lysozyme accounts for about 20% with a molecular weight of 2,500.

Papain can activate plasminogen to plasmin, targeting necrotic tissue to dissolve fibrin, blood clots, and dead matter. This action helps clean wounds, promotes new granulation tissue growth, aids in pus and fluid drainage, and accelerates healing.