Papain papain is a thiol protease with broad substrate specificity, the role of L-arginine in the protein, L-lysine, glycine and L-melon papain 
 Carboxylic acid residues involved in the formation of the peptide bond. This enzyme is a endopeptidase, whole egg protein molecules can be cut within the peptide chain-CO-NH-generation low molecular weight of the peptide. Endosperm present in papaya protease. EC3.4.22.2. As a plant source of protease, the enzyme of this progress the fastest. This enzyme is mainly within the peptide form of the enzyme works. Production activity, while cysteine ??residues is indispensable, it is a sulfur-based protease substrate specificity is not strict, the molecular weight of 23,400, 212 amino acid residues. Papain is a kind of acidic, neutral and alkaline conditions can break down protein protease. Its appearance is white to light yellow powder, slight moisture absorption. Casein degradation by papain in the ultraviolet region generated tyrosine absorption peak at 275nm. Papain (Papain) referred to as papaya enzyme, also known as papaya enzyme. Is the use of unripe papaya (Carica papaya) fruit in the milk, the use of modern biotechnology extracted from the natural enzyme products. It is a containing mercapto (-SH) endopeptidase enzyme with protease and esterase activity, have a broader specificity of the animal and plant protein, peptide, ester, amide hydrolysis, which are strong, also has the synthesis, the synthesis of protein hydrolysates can type protein. Soluble in water and glycerin, a colorless or pale yellow solution, sometimes milky white; almost insoluble in organic solvents. The most suitable PH value 6-7 (usually 3 to 9.5 can be), when in neutral or acidic is also the role of the isoelectric point (pI) of 8.75; the most suitable temperature is 55 ~ 65 ℃ (10 ~ 85 ℃ are generally available), heat resistance at 90 ℃ when not completely inactivated; inhibited by oxidants, reducing agents activate.