Papain is a proteolytic enzyme that belongs to the protease group and can be produced in considerable quantities by the roots, stems, leaves and fruits of the papaya tree (Carica papaya, Caricaceae).  Papain, a cysteine protease resides in the latex of the papaya tree and provides defence against the larvae of lepidopterans such as the oligophagous Samia ricini (Saturniidae) and two notorious polyphagous pests, Mamestra brassicae (Noctuidae) and Spodoptera litura (Noctuidae) (1).

Industrially it occurs as a fine white or yellowish powder soluble in water and glycerine, almost insoluble in organic solvents such as ethanol, chloroform and ether.

What it is used for and where

In the human body it functions as an aid in the digestive process and is a remarkable antioxidant. it can synthesise proteolytic compounds into protein-like compounds.

Medicine

It can improve wound healing with alginate dressings, thus aggregating the healing properties of both substances (2).

Cell cultures

In the preparation of cell cultures to separate cells. 

Food

Can hydrolyse macromolecular proteins in food into small molecular peptides or easily absorbed amino acids, widely used in chicken, pork, beef and other animals, seafood, soybean, peanut. Used as a meat tenderizer, wine clarifying agent, biscuit loosening agent, stabiliser, soy sauce fermenter and wine fermenting agent.

In confectionery products, it tends to reduce the moist tendon degree of dough, improve dough plasticity and physical and chemical properties, at the same time make protein macromolecular hydrolysis into short peptide and amino acid, so that the colour of the product is pleasing to the eye with a bright patina.

Cosmetics

Performs various functions depending on the percentage included in the formula. It can improve skin elasticity, remove stains and dirt, disinfect.

Other uses

Additive in animal feeds as a protein source for development and increase feed utilisation rate by aiding animal digestion.

In the leather industry as a depilatory agent, in wool treatment and silk refining, may have softening functions.

Papain studies

Typical commercial product characteristics Papain

• Formula molecolare  C₉H₁₄N₄O₃
• Peso molecolare     226.23
• CAS  9001-73-4
• UNII    A236A06Y32
• EC Number   232-627-2
• DSSTox Substance ID  DTXSID7044184
• IUPAC  2-(3-azaniumylpropanoylamino)-3-(1H-imidazol-5-yl)propanoate
• InChI=1S/C9H14N4O3/c10-2-1-8(14)13-7(9(15)16)3-6-4-11-5-12-6/h4-5,7H,1-3,10H2,(H,11,12)(H,13,14)(H,15,16)
• InChl Key      CQOVPNPJLQNMDC-UHFFFAOYSA-N
• SMILES   C1=C(NC=N1)CC(C(=O)[O-])NC(=O)CC[NH3+]
• MDL number  MFCD00131791
• PubChem Substance ID    
• ChEBI  
• NACRES NA.54   
• eCl@ss   42030311
• RTECS   
• UN   
• NCI   

Synonyms:

• 2-(3-azaniumylpropanoylamino)-3-(1H-imidazol-5-yl)propanoate

References______________________________________________________________________

(1) Konno K, Hirayama C, Nakamura M, Tateishi K, Tamura Y, Hattori M, Kohno K. Papain protects papaya trees from herbivorous insects: role of cysteine proteases in latex. Plant J. 2004 Feb;37(3):370-8. doi: 10.1046/j.1365-313x.2003.01968.x. 

(2) Moreira Filho RNF, Vasconcelos NF, Andrade FK, Rosa MF, Vieira RS. Papain immobilized on alginate membrane for wound dressing application. Colloids Surf B Biointerfaces. 2020 Oct;194:111222. doi: 10.1016/j.colsurfb.2020.111222.