Papain
Encyclopedia
Papain, also known as papaya proteinase I, is a cysteine protease
enzyme
present in papaya
(Carica papaya) and mountain papaya
(Vasconcellea cundinamarcensis).
s, aminopeptidase
s, dipeptidyl peptidase
s 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 (zymogen
s) 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.
. Its three-dimensional structure consists of two distinct structural domains with a cleft between them. This cleft contains the active site
, which contains a catalytic diad that has been likened to the catalytic triad
of chymotrypsin
. The catalytic diad is made up of the amino acids - cysteine-25 (from which it gets its classification) and histidine-159. Aspartate-158 was thought to play a role analogous to the role of aspartate in the serine protease
catalytic triad, but that has since then been disproved. Nonetheless, it does appear to play a role.
s involves deprotonation of Cys-25 by His-159. Asparagine-175 helps to orient the imidazole
ring of His-159 to allow this deprotonation to take place. Cys-25 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
.
treatment for jellyfish
, bee
, and yellow jacket (wasps) stings; mosquito
bites; and possibly stingray
wounds, breaking down the protein toxins in the venom.
Papain can be used to dissociate cells in the first step of cell culture
preparations. A ten-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 ten 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 pipette
) to break up the pieces of tissue into a single cell suspension.
It is also used as an ingredient in various enzymatic
debriding
preparations, notably Accuzyme. These are used in the care of some chronic wounds to clean up dead tissue.
Papain can also be found as an ingredient in some toothpastes or mints as teeth-whitener. Its whitening effect in toothpastes and mints is minimal, however, because the papain is present in low concentrations, and is quickly diluted by saliva. It would take several months of using the whitening product to have noticeably whiter teeth.
It is the main ingredient of Papacarie, a gel used for chemomechanical dental caries
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.
Papain has been known to interfere with urine drug test for cannabinoids. It is found in some drug detox products.
An antibody
digested by papain yields three fragments: two 50 kDa Fab fragments and one 50kDa Fc fragment. The papain-digested antibody is unable to promote agglutination
, precipitation
, opsonization, and lysis
.
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.
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. Author, director, Office of Compliance for CDER, FDA.
TSC; CTSF
; CTSH; CTSK; CTSL1
; CTSL2
;
CTSL3; CTSO; CTSS
; CTSW; CTSZ
; TINAG
; TINAGL1
;
Cysteine protease
Proteases are enzymes that degrade polypeptides. Cysteine proteases have a common catalytic mechanism that involves a nucleophilic cysteine thiol in a catalytic dyad. 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...
enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
present in papaya
Papaya
The papaya , papaw, or pawpaw is the fruit of the plant Carica papaya, the sole species in the genus Carica of the plant family Caricaceae...
(Carica papaya) and mountain papaya
Mountain papaya
The mountain papaya, Vasconcellea pubescens, also known as mountain paw paw, 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 m...
(Vasconcellea cundinamarcensis).
Papain family
Papain belongs to a family of related proteins with a wide variety of activities, including endopeptidaseEndopeptidase
Endopeptidase or endoproteinase are proteolytic peptidases that break peptide bonds of nonterminal amino acids , in contrast to exopeptidases, which break peptide bonds from their end-pieces. For this reason, endopeptidases cannot break down peptides into monomers, while exopeptidases can break...
s, aminopeptidase
Aminopeptidase
Aminopeptidase is a zinc-dependent enzyme produced and secreted by glands of the small intestine. It helps the enzymatic digestion of proteins. Additional digestive enzymes produced by these glands include dipeptidases, maltase, sucrase, lactase, and enterokinase.Aminopeptidases catalyze the...
s, dipeptidyl peptidase
Dipeptidyl peptidase
Dipeptidyl peptidase is a type of enzyme classified under EC 3.4.14.Types include:* Cathepsin C, dipeptidyl peptidase-1* DPP3, dipeptidyl peptidase-3* Dipeptidyl peptidase-4* DPP6, dipeptidyl peptidase-6* DPP7, dipeptidyl peptidase-7...
s 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 (zymogen
Zymogen
A zymogen is an inactive enzyme precursor. A zymogen requires a biochemical change for it to become an active enzyme. The biochemical change usually occurs in a lysosome where a specific part of the precursor enzyme is cleaved in order to activate it...
s) 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.
Structure
The papain precursor protein contains 345 amino acid residues, and consists of a signal sequence (1-18), a propeptide (19-133) and the mature peptide (134-345). The amino acid numbers are based on the mature peptide. The protein is stabilised by three disulfide bridgesDisulfide bond
In 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 R-S-S-R. The terminology is widely used in biochemistry...
. Its three-dimensional structure consists of two distinct structural domains with a cleft between them. This cleft contains the active site
Active site
In biology the active site is part of an enzyme where substrates bind and undergo a chemical reaction. The majority of enzymes are proteins but RNA enzymes called ribozymes also exist. The active site of an enzyme is usually found in a cleft or pocket that is lined by amino acid residues that...
, which contains a catalytic diad that has been likened to the catalytic triad
Catalytic triad
A 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...
of chymotrypsin
Chymotrypsin
Chymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin preferentially cleaves peptide amide bonds where the carboxyl side of the amide bond is a tyrosine, tryptophan, or phenylalanine. These amino acids contain an aromatic ring in their sidechain that fits into a...
. The catalytic diad is made up of the amino acids - cysteine-25 (from which it gets its classification) and histidine-159. Aspartate-158 was thought to play a role analogous to the role of aspartate in the serine protease
Serine protease
Serine proteases are enzymes that cleave peptide bonds in proteins, in which serine serves as the nucleophilic amino acid at the active site.They are found ubiquitously in both eukaryotes and prokaryotes...
catalytic triad, but that has since then been disproved. Nonetheless, it does appear to play a role.
Function
The mechanism by which it breaks peptide bondPeptide bond
This article is about the peptide link found within biological molecules, such as proteins. A similar article for synthetic molecules is being created...
s involves deprotonation of Cys-25 by His-159. Asparagine-175 helps to orient the imidazole
Imidazole
Imidazole is an organic compound with the formula C3H4N2. This aromatic heterocyclic is a diazole and 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 nucleophilic
Nucleophile
A nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...
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
Arginine
Arginine is an α-amino acid. The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that codify for arginine during...
or Lys
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
)- cleaves here -(not Val
Valine
Valine is an α-amino acid with the chemical formula HO2CCHCH2. L-Valine is one of 20 proteinogenic amino acids. Its codons are GUU, GUC, GUA, and GUG. This essential amino acid is classified as nonpolar...
). Hydrophobic is Ala
Alanine
Alanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
, Val
Valine
Valine is an α-amino acid with the chemical formula HO2CCHCH2. L-Valine is one of 20 proteinogenic amino acids. Its codons are GUU, GUC, GUA, and GUG. This essential amino acid is classified as nonpolar...
, Leu
Leucine
Leucine is a branched-chain α-amino acid with the chemical formula HO2CCHCH2CH2. Leucine is classified as a hydrophobic amino acid due to its aliphatic isobutyl side chain. It is encoded by six codons and is a major component of the subunits in ferritin, astacin and other 'buffer' proteins...
, Ile
Isoleucine
Isoleucine is an α-amino acid with the chemical formula HO2CCHCHCH2CH3. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested. Its codons are AUU, AUC and AUA....
, Phe
Phenylalanine
Phenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...
, Trp
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
, or Tyr
Tyrosine
Tyrosine or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. Its codons are UAC and UAU. It is a non-essential amino acid with a polar side group...
.
Uses
Its utility is in breaking down tough meat fibres and has been used for thousands of years in its native South America. It is sold as a component of powdered meat tenderiser available in most supermarkets. Papain, in the form of such a powdered meat tenderizer, made into a paste with water, is also a home remedyHome remedy
A 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 jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
, bee
Bee
Bees 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...
, and yellow jacket (wasps) stings; mosquito
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...
bites; and possibly stingray
Stingray
The stingrays are a group of rays, which are cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families: Hexatrygonidae , Plesiobatidae , Urolophidae , Urotrygonidae , Dasyatidae , Potamotrygonidae The...
wounds, breaking down the protein toxins in the venom.
Papain can be used to dissociate cells in the first step of cell culture
Cell culture
Cell culture is the complex 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 singlecellular eukaryotes, especially animal cells. However, there are also cultures of plants, fungi and microbes,...
preparations. A ten-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 ten 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 pipette
Pasteur pipette
Pasteur 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...
) to break up the pieces of tissue into a single cell suspension.
It is also used as an ingredient in various enzymatic
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
debriding
Debridement
Debridement 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.
Papain can also be found as an ingredient in some toothpastes or mints as teeth-whitener. Its whitening effect in toothpastes and mints is minimal, however, because the papain is present in low concentrations, and is quickly diluted by saliva. It would take several months of using the whitening product to have noticeably whiter teeth.
It is the main ingredient of Papacarie, a gel used for chemomechanical dental caries
Dental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...
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.
Papain has been known to interfere with urine drug test for cannabinoids. It is found in some drug detox products.
Immunoglobulins
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
digested by papain yields three fragments: two 50 kDa Fab fragments and one 50kDa Fc fragment. The papain-digested antibody is unable to promote agglutination
Agglutination
In contemporary linguistics, agglutination usually refers to the kind of morphological derivation in which there is a one-to-one correspondence between affixes and syntactical categories. Languages that use agglutination widely are called agglutinative languages...
, precipitation
Protein precipitation
Precipitation 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 lysis
Lysis
Lysis refers to the breaking down of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a "lysate"....
.
Production
Papain is usually produced as a crude, dried material by collecting the latexLatex
Latex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...
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 (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. Author, director, Office of Compliance for CDER, FDA.
Human cysteine proteases from papain family
CTSB; CCathepsin C
Cathepsin C also known as dipeptidyl peptidase I is a lysosomal exo-cysteine protease belonging to the peptidase C1 family...
TSC; CTSF
CTSF
Cathepsin F is a protein that in humans is encoded by the CTSF gene.-External links:* The MEROPS online database for peptidases and their inhibitors:...
; CTSH; CTSK; CTSL1
CTSL1
Cathepsin L1 is a protein that in humans is encoded by the CTSL1 gene.-Interactions:CTSL1 has been shown to interact with Cystatin A.-External Links:* The MEROPS online database for peptidases and their inhibitors:...
; CTSL2
CTSL2
Cathepsin L2, also known as cathepsin V and encoded by the CTSL2 gene, is a human gene.The protein encoded by this gene, a member of the peptidase C1 family, is a lysosomal cysteine proteinase that may play an important role in corneal physiology...
;
CTSL3; CTSO; CTSS
Cathepsin S
Cathepsin S, also known as CTSS, is a protein which in humans is encoded by the CTSS gene.The protein encoded by this gene, a member of the peptidase C1 family, is a lysosomal cysteine protease that may participate in the degradation of antigenic proteins to peptides for presentation on MHC class...
; CTSW; CTSZ
CTSZ
Cathepsin Z or cathepsin X is a protein that in humans is encoded by the CTSZ gene.-External links:* The MEROPS online database for peptidases and their inhibitors:...
; TINAG
TINAG
Tubulointerstitial nephritis antigen is a protein that in humans is encoded by the TINAG gene.-Further reading:...
; TINAGL1
TINAGL1
Tubulointerstitial nephritis antigen-like is a protein that in humans is encoded by the TINAGL1 gene.-Further reading:...
;
External links
- The MEROPSMeropsMerops may refer to:* Merops , a genus of bee-eaters.* MEROPS, an on-line database for peptidases.It may also refer to several figures from Greek mythology:* King of Ethiopia, husband of Clymene, who lay with Helios and bore Phaethon...
online database for peptidases and their inhibitors: C01.001 - drugdigest- info on papin
- Papain Applications, Inhibitors and Substrates
- Data sheet-Papain from BIOZYM