Papain is a
cysteine proteaseProteases are enzymes that degrade polypeptides. Cysteine proteases have a common catalytic mechanism that involves a nucleophilic cysteine thiol in a catalytic triad. The first step is deprotonation of a thiol in the enzyme's active site by an adjacent amino acid with a basic side chain, usually a...
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at...
present in
papayaThe papaya is the fruit of the plant Carica papaya, in the genus Carica. It is native to the tropics of the Americas, and was cultivated in Mexico several centuries before the emergence of the Mesoamerican classic cultures...
(
Carica papaya) and
mountain papayaThe Mountain Papaya , is a species of the genus Vasconcellea, native to the Andes of northwestern South America from Colombia south to central Chile, typically growing at altitudes of 1,500-3,000 m...
(
Vasconcellea cundinamarcensis).
It consists of 212
amino acidAmino acids are molecules containing an amine group, a carboxylic acid group and one of the twenty R-groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H
2NCHRCOOH, where R is an organic substituent...
s stabilised by 3
disulfide bridgesIn chemistry, a disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore C-S-S-C. The terminology is widely used in biochemistry...
. Its 3D structure consists of 2 distinct structural domains with a cleft between them. This cleft contains the
active siteThe active site of an enzyme contains the catalytic and binding sites. The structure and chemical properties of the active site allow the recognition and binding of the substrate....
, which contains a
catalytic triadA catalytic triad refers to the three amino acid residues found inside the active site of certain protease enzymes: serine , aspartate , and histidine . They work together to break peptide bonds on polypeptides. In general terms, catalytic triad can refer to any set of three residues that function...
that has been likened to that of
chymotrypsinChymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin cleaves peptides at the carboxyl side of tyrosine, tryptophan, and phenylalanine because these three amino acids contain aromatic rings, which fit into a 'hydrophobic pocket' in the enzyme...
. Its catalytic triad is made up of 3 amino acids - cysteine-25 (from which it gets its classification), histidine-159, and asparagine-158.
The mechanism by which it breaks
peptide bondA peptide bond is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amine group of the other molecule, thereby releasing a molecule of water . This is a dehydration synthesis reaction, and usually occursbetween amino acids...
s involves deprotonation of Cys-25 by His-159.
Papain is a
cysteine proteaseProteases are enzymes that degrade polypeptides. Cysteine proteases have a common catalytic mechanism that involves a nucleophilic cysteine thiol in a catalytic triad. The first step is deprotonation of a thiol in the enzyme's active site by an adjacent amino acid with a basic side chain, usually a...
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at...
present in
papayaThe papaya is the fruit of the plant Carica papaya, in the genus Carica. It is native to the tropics of the Americas, and was cultivated in Mexico several centuries before the emergence of the Mesoamerican classic cultures...
(
Carica papaya) and
mountain papayaThe Mountain Papaya , is a species of the genus Vasconcellea, native to the Andes of northwestern South America from Colombia south to central Chile, typically growing at altitudes of 1,500-3,000 m...
(
Vasconcellea cundinamarcensis).
Structure
It consists of 212
amino acidAmino acids are molecules containing an amine group, a carboxylic acid group and one of the twenty R-groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H
2NCHRCOOH, where R is an organic substituent...
s stabilised by 3
disulfide bridgesIn chemistry, a disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore C-S-S-C. The terminology is widely used in biochemistry...
. Its 3D structure consists of 2 distinct structural domains with a cleft between them. This cleft contains the
active siteThe active site of an enzyme contains the catalytic and binding sites. The structure and chemical properties of the active site allow the recognition and binding of the substrate....
, which contains a
catalytic triadA catalytic triad refers to the three amino acid residues found inside the active site of certain protease enzymes: serine , aspartate , and histidine . They work together to break peptide bonds on polypeptides. In general terms, catalytic triad can refer to any set of three residues that function...
that has been likened to that of
chymotrypsinChymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin cleaves peptides at the carboxyl side of tyrosine, tryptophan, and phenylalanine because these three amino acids contain aromatic rings, which fit into a 'hydrophobic pocket' in the enzyme...
. Its catalytic triad is made up of 3 amino acids - cysteine-25 (from which it gets its classification), histidine-159, and asparagine-158.
Function
The mechanism by which it breaks
peptide bondA peptide bond is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amine group of the other molecule, thereby releasing a molecule of water . This is a dehydration synthesis reaction, and usually occursbetween amino acids...
s involves deprotonation of Cys-25 by His-159. Asp-158 helps to orient the
imidazoleImidazole is an organic compound with the formula C3H4N2. This aromatic heterocyclic is classified as an alkaloid. Imidazole refers to the parent compound whereas imidazoles are a class of heterocycles with similar ring structure but varying substituents...
ring of His-159 to allow this deprotonation to take place. Cys-25 then performs a
nucleophilicIn chemistry, a nucleophile is a reagent that forms a chemical bond to its reaction partner by donating both bonding electrons. Because nucleophiles donate electrons, they are by definition Lewis bases . All molecules or ions with a free pair of electrons can act as nucleophiles...
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.
Uses
Its utility is in breaking down tough meat fibers and has been utilized for thousands of years in its native South America. It is sold as a component in powdered meat tenderizer available in most supermarkets. Papain, in the form of a meat tenderizer such as Adolph's, made into a paste with water, is also a
home remedyA home remedy is a treatment to cure a disease or ailment that employs certain spices, vegetables, or other common items. Home remedies may or may not have medicinal properties that treat or cure the disease or ailment in question, as they are typically passed along by laypersons...
treatment for
jellyfishJellyfish are free-swimming members of the phylum Cnidaria. Jellyfish have several different morphologies that represent several different cnidarian classes including the Scyphozoa , Staurozoa , Cubozoa , and Hydrozoa Jellyfish (also known as jellies or sea jellies) are free-swimming members of...
,
beeBees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...
, yellow jacket (wasps) stings,
mosquitoMosquito is a common insect in the family Culicidae...
bites, and possibly
stingrayThe stingrays are a family—Dasyatidae—of rays, cartilaginous fishes related to sharks. They are common in coastal tropical and subtropical marine waters throughout the world, but the family also includes species found in warmer temperate oceans such as Dasyatis thetidis, and species entirely...
wounds, breaking down the protein toxins in the venom. It is also the main ingredient in Stop Itch and Stop Itch Plus, a DermaTech Laboratories first aid cream popular in Australia.
Papain can be used to dissociate cells in the first step of
cell cultureCell culture is the process by which cells are grown under controlled conditions. In practice the term "cell culture" has come to refer to the culturing of cells derived from multicellular eukaryotes, especially animal cells...
preparations. A 10-minute treatment of small tissue pieces (less than 1 mm cubed) will allow papain to begin breaking down the extracellular matrix molecules holding the cells together. After 10 minutes, the tissue should be treated with a protease inhibitor solution to stop the protease action (if left untreated papain's activity will lead to complete lysis of the cells). The tissue must then be triturated (passed quickly up and down through a
Pasteur pipettePasteur pipettes, also known as droppers or eye droppers, are used to transfer small quantities of liquids. They are usually glass tubes tapered to a narrow point, and fitted with a rubber bulb at the top. The combination of the Pasteur pipette and rubber bulb has also been referred to as a teat...
) in order to break up the pieces of tissue into a single cell suspension.
It is also used as an ingredient in various
enzymaticEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at...
debridingDebridement is the medical removal of a patient's dead, damaged, or infected tissue to improve the healing potential of the remaining healthy tissue...
preparations, notably Accuzyme. These are used in the care of some chronic wounds to clean up dead tissue.
It can also be found as an ingredient in some toothpastes or mints as teeth-whitener. Its whitening effect in toothpastes and mints however is minimal, because the papain is present in low concentrations, and will be quickly diluted by saliva. It would take several months of using the whitening product to have noticeably whiter teeth.
Papain is the main ingredient of Papacarie, a gel used for chemomechanical
dental cariesDental caries, also known as tooth decay or cavity, is a disease wherein bacterial processes damage hard tooth structure . These tissues progressively break down, producing dental cavities . Two groups of bacteria are responsible for initiating caries: Streptococcus mutans and Lactobacilli...
removal. Besides the advantage of avoiding the use of rotary cutting tools, it does not interfere in the bond strength of restorative materials to dentin.
Immunoglobulins
An
antibodyAntibodies are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacteria and viruses...
digested by papain yields three fragments: two 50 kDa Fab fragments and one 50kDa Fc fragment. The papain-digested antibody is unable to promote
agglutinationIn linguistics, agglutination is the morphological process ofadding affixes to the base of a word. Languages that use agglutination widely are called agglutinative languages. These languages are often contrasted with fusional languages and isolating languages...
,
precipitationPrecipitation is widely used in downstream processing of biological products, such as proteins. This unit operation serves to concentrate and fractionate the target product from various contaminants. For example, in the biotechnology industry protein precipitation is used to eliminate contaminants...
, opsonization, and
lysisLysis refers to the death of a cell by breaking of the cellular membrane, causing the contents to spill out, often by viral, enzymic or osmotic mechanisms that compromise its integrity...
.
Production
Papain is usually produced as a crude, dried material by collecting the
latexLatex refers generically to a stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic. Latex as found in nature is a milky sap-like fluid within many plants that coagulates on exposure to air. It is a complex emulsion in which proteins, alkaloids,...
from the fruit of the papaya tree. The latex is collected after scoring the neck of the fruit where it may either dry on the fruit or drip into a container. This latex is then further dried. It is now classified as a dried, crude material. A purification step is necessary to remove contaminating substances. This purification consists of the solubilization and extraction of the active papain enzyme system through a government-registered process. This purified papain may be supplied as powder or as liquid.
Action by the FDA to restrict marketing of all topical drug products containing papain
- See also article: Proteases (medical and related uses)
Proteases are in use, or have been proposed or tried, for a number of purposes related to medicine or surgery. Some preparations involving protease have undergone successful clinical trials and have regulatory authorization; and some further ones have shown apparently useful effects in...
On September 23, 2008, the FDA warned companies to stop marketing topical drug products containing papain by November 4, 2008. The FDA said, "Papain-containing drug products in topical form historically have been marketed without approval...". According to the FDA's statement on the subject, "These unapproved products have put consumers' health in jeopardy, from reports of permanent vision loss with unapproved balanced salt solutions to a serious drop in blood pressure and increased heart rate from the topical papain products," said Janet Woodcock, M.D., director for the Center for Drug Evaluation and Research. In the same FDA announcement, the FDA states the following:
About Unapproved Topical Papain Products:
Topical drug ointments containing papain are used to remove dead or contaminated tissue in acute and chronic lesions, such as diabetic ulcers, pressure ulcers, varicose ulcers, and traumatic infected wounds. Trade names for these products include Accuzyme, Allanfil, Allanzyme, Ethezyme, Gladase, Kovia, Panafil, Pap Urea, and Ziox. Other products are marketed under the names of the active ingredients, for instance, papain-urea ointment.
The FDA is taking action today against these products because it has received reports of serious adverse events in patients using products containing papain. Reports include hypersensitivity (allergic) reactions that lead to hypotension (low blood pressure) and tachycardia (rapid heart rate). In addition, patients who are allergic to latex can also be allergic to papaya, the source of papain. Therefore, patients with latex sensitivity may be at increased risk of suffering an adverse reaction to a topical papain drug product.
FDA urges consumers who are using topical drug products containing papain, and who have questions or concerns, to contact their health care provider about discontinuing treatment with these products. There are a number of FDA-approved topical products that have been found safe and effective as wound healing agents and that do not contain papain.
"Removing unapproved topical drug products containing papain and unapproved ophthalmic balanced salt solutions is yet another step forward for patient safety," said Deborah M. Autor, director, Office of Compliance for CDER, FDA.
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