Papain belongs to a family of related proteins with a wide variety of activities, including endopeptidases, aminopeptidases, dipeptidyl peptidases and enzymes with both exo- and endo-peptidase activity. Members of the papain family are widespread, found in baculovirus, eubacteria, yeast, and practically all protozoa, plants and mammals. The proteins are typically lysosomal or secreted, and proteolytic cleavage of the propeptide is required for enzyme activation, although bleomycin hydrolase is cytosolic in fungi and mammals. Papain-like cysteine proteinases are essentially synthesised as inactive proenzymes (zymogens) with N-terminal propeptide regions. The activation process of these enzymes includes the removal of propeptide regions, which serve a variety of functions in vivo and in vitro. The pro-region is required for the proper folding of the newly synthesised enzyme, the inactivation of the peptidase domain and stabilisation of the enzyme against denaturing at neutral to alkaline pH conditions. Amino acid residues within the pro-region mediate their membrane association, and play a role in the transport of the proenzyme to lysosomes. Among the most notable features of propeptides is their ability to inhibit the activity of their cognate enzymes and that certain propeptides exhibit high selectivity for inhibition of the peptidases from which they originate.
Function of Papain
The mechanism by which papain breaks peptide bonds involves the use of a catalytic triad with a deprotonated cystine. Asn-175 helps to orient the imidazole ring of His-159 to allow it to deprotonate the catalytic Cys-25. This cysteine then performs a nucleophilic attack on the carbonyl carbon of a peptide backbone. This frees the amino terminal of the peptide, and forms a covalent acyl-enzyme intermediate. The enzyme is then deacylated by a water molecule, and releases the carboxy terminal portion of the peptide. In immunology, papain is known to cleave the Fc (crystallisable) portion of immunoglobulins (antibodies) from the Fab (antigen-binding) portion.
Papain is a relatively heat resistant enzyme, with a temperature optimal range of 60-70 °C.
Papain prefers to cleave at: (hydrophobic)-(Arg or Lys)- cleaves here -(not Val). Hydrophobic is Ala, Val, Leu, Ile, Phe, Trp, or Tyr.
THE AFTER MEAL SUPPLEMENT®
Each pleasantly small, delicious, chewable fruit flavored Papaya tablet contains the enzyme papain. Starch- & preservative-free!
No Artificial Color, No Preservatives, No Milk, No Lactose, No Soy, No Gluten, No Wheat, No Yeast, No Fish, Sodium Free.
Serving Size 3 Tablets
Servings Per Container 33
Amount Per Serving
% Daily Value
1 g < 1%**
< 1 g ***
157 mg 16%
45 mg ***
6 mg ***
6 mg ***
3 mg ***
**Percent Daily Values are based on a 2,000 calorie diet.
***Daily Value not established.
Directions: For adults, chew three (3) tablets following a meal, one to three times daily.
WARNING: If you are pregnant, nursing, taking any medications or have any medical condition, consult your doctor before use. Discontinue use and consult your doctor if any adverse reactions occur. KEEP OUT OF REACH OF CHILDREN. STORE AT ROOM TEMPERATURE. DO NOT USE IF SEAL UNDER CAP IS BROKEN OR MISSING.